It's there between the lines in the on-topic page between these two bullet points:
identifying a song, style/genre, instrument/equipment, technique, chord progression, etc.
identifying notes/chords/meters in your favourite song
It's not the clearest, but it is there. After a review of the history of the on-topic page it was there until we made analysis on topic. It's a good point that transcription should be mentioned by name, so I've slightly tweaked what we have in the second bullet point to:
transcription of specific works including identifying
notes/chords/meters in your favourite song
We don't have control over the don't ask page it is an SE standard as you can see it the exact same on other sites. It's just talking about the general SE policy across all SE sites. It's pretty flexible how it's applied from site to site and the on-topic section is much more important.
This was not the first time this discussion was brought up. Ever since analysis was allowed it's been pointed out we don't do transcription.