Half of all green dots change to orange

I’ve searched your KB and the forums and can’t find an answer, so here goes.

I’ve followed Yoast SEO recommendations to achieve green dots across the board, for a client. Months later, I see that about half of the dots (~50 of 100) have turned to orange (no post edits involved). I’m curious why this might happen, and anticipate questions from the client (and additional time).

Was a recent Yoast SEO algorithm change related to a Google update – contributing to the green to orange shift? Can you point me to a blog post or changelog that might explain it? TIA!