https://4dayweek.io/blog/the-ultimate-guide-to-the-4-day-wor...
I too still find it weird why more companies don't offer at least a 4 day week @ 80% salary
The biggest resistance I get is around this "part time/full time" divide. They basically think that 4 days = part-time, which usually means a temp or entry-level person. They argue that the work isn't the kind of work that should be classified as part-time. It takes lots of convincing to say that this is still full-time.
I've been thinking of writing some sort of guide around all the various arguments I get and ways I've implemented it at previous employers...