Interesting that nothing you say here actually contradicts my posts. I'm aware that Marr put harmonic progressions and structures onto tapes for Morrissey - that's pretty much what I said - and that Morrissey, as you say, and as I said, then wrote a vocal line and words. We both agree that Marr then added stuff in the studio and that neither of us know if he gave pointers to Rourke (but I'll lay odds he didn't - you only have to listen to the intricacy and idiosyncratic quality of those bass lines to realise that).
So what's your point exactly?
Ah yes, you think this demonstrates that the songs were 'co-written'. They weren't. They were created when Morrissey, as you say, put down his vocal line and words. 'Bigmouth Strikes Again' is 'Bigmouth Strikes Again' because of the vocal melody and words. Give the same backing track to a different lyricist/vocalist (even assuming the backing track was in its finished state which, as you yourself acknowledge, it probably wasn't) and you'd have a completely different song.
"a lack of understanding of how a song is written in general" is a fatuous remark since songs are written/created in various ways, not according to some 'industry standard'. Lennon and McCartney co-wrote some songs sitting face to face with their guitars in hand. Sometimes they pieced together individual parts they'd already written. Elton John put music and vocal melodies to Bernie Taupin's lyrics. Some songwriters read music and literally 'write' music; most don't and the term song'writing' in reference to anything other than the lyrics is therefore in those cases not literal. Morrissey didn't 'write' his vocal melodies, and Marr didn't 'write' his music.
The public record you're referring to is presumably Marr's account, and Morrissey's, of how the songs were created. Nobody's disputing that what they say is true in so far as it goes - yes, Marr recorded backing tracks and gave them to Morrissey. What's in dispute is whether he deserved a songwriting co-credit for that (he didn't) and whether Rourke ought to have a had a co-writing music compositional credit for the finished backing tracks (he should have).
To simply accept Marr's and Morrissey's accounts at face value is being a little credulous and displays a lack of understanding of how songs are 'written' in general.
In other words, your argument is horse shit.