I've noticed on all 3 of my web properties (websites) that one by one, as they were reindexed to the Mobile-first Index the 2 different Crawl Error categories of Desktop and Smart Phone merged into one.

I have also noticed that for these 3 sites, there have been no crawl errors logged since (between 4 to 6 months.)

Surely those broken backlinks still exist, so Google must have changed how they attribute and/or define a crawl error now.

If so, this is good news. I've always found it irritating for Google to list something I have no control over as an error at my website, especially since they had stopped identifying where the error was found.