> I remember there were mixed 68k/PPC elfs even

No, there were not.

"Problem with ELF binary format was that [...] mixing PPC/68k code was not possible. Extended Hunk Format (EHF), developed by Haage & Partner, allowed mixing PPC and 68k code to single executable without modifying the existing system if PowerPC accelerator was not installed."
https://en.wikipedia.org/wiki/Amiga_Hunk#Extended_Hunk_format

> I see warp datatypes [...] were endeed OS4 ported

...as well as to OS3/m68k and MorphOS.