Indeed, Post #20 nails it. If the spring "stacks" or in some other way becomes "stiff", whatever I mean by that, the energy remaining the slide has to be absorbed by those thin tabs that the spring bears against.

It would be interesting for someone with the proper tools, and a variety of OEM and replacement springs available, to measure the length (distance between the end flanges) when the springs are compressed to a fully closed condition, i.e. "Stacked".

Sorry if this isn't crystal clear but the test would show whether or not the various springs become a hard stop before the slide hit's it's own stop.

All this seems to now become more clear, I hope.