Important! Read if you have ILR in an expired passport

Looks like some rules changed in May and I haven't seen a post on it.  If this is a duplicate, please ignore.   

UKVI is now saying that if you have an expired non-UK passport that is being used to prove ILR, it is no longer acceptable and that you must transfer your conditions for a BRP (for employment purposes).

I'm also wondering if this new rule is what caused a USC to recently be stamped into the UK as a visitor after obtaining naturalisation with a vignette (on Facebook) and phatbeetle's trouble with her BRP recently...

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/313849/employers_guide_to_acceptable_right_to_work_documents.pdf

There may well be something to this, but my reading of the document linked is a bit different. First, this seems to be about proving a right to work, not entering the country. Also, I see the word "solely" regarding an expired passport. If you have a current passport endorsed on entry with "vipp" or "visa in previous passport" then the employer would be relying on that, rather than "solely" the expired one. No?

If there's more to it though, please do let us know!