Sorry Helio, but there is way too much information out there that Mannerheim had no interest at all in pushing the Russians hard beyond the original Finnish borders, especially in the Leningrad area.
There is also way too much information out there that Stalin intended to defend every inch of ground in the first 10 weeks of the war and plenty of examples of commanders being killed (as well as line troops) for retreating. Where is your outrage about the perfect zone-of-control retreat capability of the Soviet?
Your argument is invalid because you are inconsistently applying it. If you can't apply history 'everywhere' then you can't shackle either side to it anywhere. That has always been my position.
With that argument invalidated, you are faced with the stark reality of hard-coded limits imposed on Finland that produce strategically illogical AND a-historical result.
Any Colonel from any military academy would attack south toward Leningrad's back door rather than attacking eastward into what is effectively a 30-mile wide, 100-mile deep maginot line in 1941 brought about by arbitrary map edges, arbitrarily and inconsistently enforced 'political considerations' (that are only applied to the Axis when they are applied at all), and brilliant gamesmanship by people with no intention of pursuing the spirit of the rule.
You defend the indefensible.
If Mannerheim knew what would happen at Flavius's line, he would not bother to attack the Soviets at all.
What are you going to do next? Call me a Ruskie fanboy? Sorry, have had that happen and I got kicked out of the club.
That Finland has limitations in this game independent of the Germans is absolutely realistic given the independent nature of Finland and the fact they were able to exercise this independence repeatedly despite German efforts to get them to apply more pressure on the Russians. If you can't see the difference in POLITICAL limitations involving Finland and any "perfect" defense the Russians can do in this game with hindsight, then I don't know what to say except you need to step back and take a deep breath and rethink the position.
I already agreed that the map edge was an issue with its effect in an earlier post, but also noted this is often a issue in many games covering the Russian theater and the fact that games often have limitations on the Finnish theater due to game resources.
Is your goal to have no political considerations for the Finns or no stop line so they can take over a huge sector of the line during the first winter? Sort of makes that winter counter offensive a lot tougher now doesn't it? Of course in your world, you would have no issue putting in a game mechanic that allows the Germans to "ship some winter cloths to the front" and call it good about getting rid of any winter effects on the Germans despite the fact their equipment was crap in that below zero cold and even with warm cloths, the fact is the Germans were still tenderfoots in that type of element.
There are a lot of things I absolutely disagree with about this game, but having limitations on the Finns is not one of them, although like I mentioned in a earlier post, I would like to see an optional rule much like what was in FitE/Scorched Earth and the Axis take their chances about better than or worse than historical Finnish participation.