Anomie says

Screen interlace. When set in BG mode 5 (and probably 6), the
effective screen height will be 448 (or 478) pixles, rather than
224 (or 239). When set in any other mode, the screen will just get
a bit jumpy. However, toggling the tilemap each field would
simulate the increased screen height (much like pseudo-hires
simulares hires).

I read that as: in mode != 5, 6 we should not double the y coordinates.

otoh, the problem of the non-squeezing stars is probably due to missing object interlace (SETINI & 0x02) emulation. hence, no breakage on that side.

EDIT: maybe snes_dynamic_res_change shall be moved to the rendering step rather than called as soon as the bit is set...