Evening FoldCentral

Working 487 tonight, and mistakenly ran a 'BlueFuze' variant that has a 'do_mutate ()' step instead of a 'do_shake ()' - to my surprise, it actually did something. Previously, on non-mutable puzzles, the do_mutate would just skip to the next line of code, and produce a white bar on the Undo graph. So, did something get changed?

Curiosity tweaked, I ran a single line, 'do_mutate (1)' on 487, and it did a shake, but produced a light blue bar (mutate) on the Undo graph. When I run a 'select_all (), do_mutate (1), deselect_all ()' it does a shake, but produces the dark blue bar (shake) on the Undo graph.

It's well known that mutate has a shake in-built to it, but this is the first time I've actually seen it function in non-mutable puzzles. I'm happy to be shot down, but I've not seen this behaviour before.

Cheers
CFC