Definitions are tricky, and especially for terms that are broadly considered virtuous/positive by the general public (cf. “organic”) but I tend to deny something is open source unless you can recreate any binaries/output AND it is presented in the “preferred form for modification” (i.e. the way the GPLv3 defines the “source form”).

A disassembled/decompiled binary might nominally be in some programming language–suitable input to a compiler for that langauge–but that doesn’t actually make it the source code for that binary because it is not in the form the entity most enabled to make a modified form of the binary (normally or original author) would prefer to make modifications.