This isn't a simple historical issue. When military appropriations of old are used to argue in favour of this or that military policy in the present, we are dealing with history-politics – the use of history as a political tool. Sainio has an agenda in this, as his most recent book (haven't read it) clearly shows.
Personally I don't think that almost a hundred years old military policies should be used as a yardstick for any purchases now. The military does (as far as I know from having discussed this with numerous officers in the organisation) risk assessments and evaluates needs based on those.
Because it was built as such a political weapon in the first place.
Here we must return to our time old topics Russia and existential threat, you know, cornerstones of Finnish nationalism. Sainio has possibly read his history. Unfortunately for him, those histories are severely lacking on the issue of 1920s naval appropriations. By the 1930s this particular issue was done and decided, ledgers closed and what have you. Historian Martti Turtola started his career off with a banger of masters thesis in 1972. He sunk a couple of myths regarding the passing of the naval appropriations law of 1927 by showing that building the navy was always on the government agenda from 1918 onwards. Since this is an unpublished thesis locked away in the basement of University of Helsinki library, few have read it.
Turtola didn't see everything, which is why my doctoral dissertation will also discuss the events in detail. Neither he nor Sainio were maritime, technology, or economic historians. Herein lies the central issue of traditional Finnish military history. Issues are typically discussed in a vacuum. New military history has tried to puncture this myopia with cultural history, but other points of view are needed. Naval and aviation branches are quite technical. Technical issues demand expertise, resources and leadership that understands the critical need for both. I argue that the navy had all these from early 1920s onwards and this goes a long way in explaining why the submarines and ships got built.
This then begs the question, what did the army have and why weren't its efforts in developing tanks and field artillery successful? This I can't answer. Luckily my colleague Michael Halila is working on it. So check in later.
In short, the navy rebuilding program was meaningful for other actors than just the navy such as Finnish export industries (forestry in particular), merchant marine and shipbuilding industry. Civilians were and are necessary for such ambitious projects. When military men isolate themselves from the rest of society and try to control their environment single-mindedly, they may well fail to gain Society's support for their efforts. This is why various econo-industrial negotiating bodies were set up in the 1930s to create cooperation between military and civilian actors.
After the Second World War an ur-Finnish blame game got underway and the navy was an easy target for many. Pocket battleship Ilmarinen had sunk while on operations after hitting a mine. Neither it or the other ship Väinämöinen had been used as publicly argued before the war. That is as moving coastal gun batteries on the South-East coast lacking such coastal batteries. All of this was seen by non-naval types as evidence of failure. The money should have been used elsewhere. And so the myth of the greatest Finnish military mistake appropriation was created. It then persisted on and on. The history of prewar military administration was published a year after Turtola's master's thesis. In it Terä and Tervasmäki continued to permeate the myth.
Asking why the navy was successful when the army wasn't has been a taboo in Finnish military history. Interestingly Sainio places the blame on 1930s military leaders, not on their 1920s counterparts. While this might be a result of confusion and mistaken facts, it also plays into a curious tropes evident in Finnish military history. Certain parties and actors may not be criticised. This is a future task for us historians.
In my dissertation I will discuss the naval side of this complex. That will not be enough, but it will hopefully be a start. In the meantime, when you see arguments like the one I linked above, know that they are not about history but about present politics. Big technological projects have a tendency to shy away from meddlesome politics. They seem to thrive in technocracy. The 1920s and 1930s in Finland were quite different from the society we think we know now. While elite networks persist and technocrats will always be part of society, using our common day understanding will do no good in understanding the early years of Finnish independence. It is and will always remain a strange country of foreigners, where the historian threads lightly and carefully.