In short, psalm reports errors for the following examples, which are correct in fact:

https://psalm.dev/r/8972d76050 (copying a list to another list).
https://psalm.dev/r/74126f725d (appending to list end, but using an offset)
https://psalm.dev/r/fe3d1f172a (altering elements within a loop over continuous range of indices starting from 0)