Is "req" still used or present

Is “req” in note type/model still used? I can’t find it anymore in the current codebase. AnkiDroid do not use it anymore either. I prefer to check whether I change ankidroid database structure wiki whether I missed anything. I could expect it to still be present for compatibility reason, but I can’t find how f23eb350e4f608ad0ddbbcd6c99d050cb6a5af86 would ensure compatibility.
Which is strange because this commit is months before I ported this change to ankidroid in 08217dac2e11df83321ae00271d3fb03bbb3e089 so I assume anki still used “req” in some way even if I can’t figure it out.

Anki doesn’t use it, but it still writes it so that card generation (mostly) works if the user is also using an older client.