Xamk enforces new change

[mdn]

I remember other Finland university also requires similar things recently. Is this being new law/act in the Finland education system?

Briefly yes, due to the financial situation and future changes, for example: https://yle.fi/a/74-20089083

Might be later it will be improved somehow for EU/EEA students.

I was hoping they would continue offering their open university courses to foreigners if they paid the tuition, but it seems like they did this instead.

15 EUR per ECTS - definitely considered as subsidized, as at least 10000 EUR per year per 60 credits = ~167 EUR per credit. Also it had been said multiple times that the current tuition fee in 10-12k EUR per year does not "cover the full cost of education."