I seem to remember that TC or NAV Can put out a publication or circular on not using the word "for" when reporting in a climb or descent.

Don't say this: "Call-sign XXX, 3-3-0 for 3-6-0"

Say this: "Call-sign, 3-3-0 climbing 3-6-0"

Does anyone recall this? Reference?

Didn't they do it for two as well?

"Descend to one two thousand...Descend one two thousand"

CAP413 refers to use of "TO" with altitude and flight level in section 3.9. Doesn't appear to say anything about "FOR" though.

This eurocontrol document:
https://www.skybrary.aero/bookshelf/books/115.pdf
says something about it on page 16, but it's not exactly what the OP asked for.