Note that the proposal for this came from the EU Commission over the last few years - the Trans-European Transport Network (TEN-T). Initially Finland pushed back on it as being too expensive.
https://transport.ec.europa.eu/transport-themes/infrastructu...
There is little benefit for the cost for Finland. Currently I believe that there are no railway between Finland and the rest of the EU, with the first one to Sweden under construction (and obviously a huge detour since the only land connection is through the North of the country).
The connection between Finland and Sweden was built in 1919, however it was recently electrified(January 2025). It's dual gauge(four rails).
Ok so it's passengers link that is under development. Doesn't change the big picture, though.