This is total nonsense. Finland does not constitute a threat to Russia and is free to act as it wishes.If the Finns attempted to join NATO now, there is a major risk of a pre-emptive Russian strike which could lead to Helsinki resembling Mariupol today. That would be an avoidable tragedy. Finland has had a modus vivendi with the USSR/Russia since the end of WW2 and it would be foolish to destabilise this arrangement. Unlike Ukraine, Finland is essentially physically separated from the rest of Europe by the Gulf of Bothnia, but has a very long land border with Russia, so is vulnerable to a well-organised Russian attack, as in 1944; once the Finns' military supplies are exhausted, it would be difficult to replenish them from abroad.
Finland is not separated from Europe, it is attached to Sweden and Norway and a short flight or sail from Sweden or Estonia.
Russia don't do well-organised attacks. If the Ukrainians can hold off the Russians, so can the Finns because the terrain and road network is much more favourable to the defender in that area- as the Soviets found out. And the long land border works both ways- Finland could cut off Murmansk from the rest of Russia if it wished (although I am not recommending that course of action).