Minnesotan here. I don’t agree with this statement. Although the vast majority of lakes do have some spring water feed, it doesn’t usually create a weak spot in the ice. Typically lake ice weak spots are at water inflows and outflows from rivers, and these are almost always marked with stakes. The lakes are quite safe to travel on, especially when snow build-up occurs and only plowed roads are traveled by heavy equipment (and the plowed roads are always such that they avoid weak spots). That being said every year people do fall through, but that’s almost always operator error.