Actually going to answer my own question, because looking at various questions about this, I suspect many didn’t know what the issue is, as some were just saying it didn’t work.
It’s quite a simple one. When exporting, obviously have BWAV selected, but on the left there’s a checkbox marked “Add BWAV Chunk”.
Check that, and your bounced mixes and stems will be timecode stamped.
Well mine were anyway.
Rob