Very cool, if true

I think that bit is being over-egged a bit.
The Cabinet Manual says:
"Recent examples suggest that previous Prime Ministers have not offered their resignations until there was a situation in which clear advice could be given to the Sovereign on who should be asked to form a government"
but it follows that up with
"It remains to be seen whether or not these examples will be regarded in future as having established a constitutional convention."

So I think she _can_ leave, but that it's expected that she'll hang about until she can recommend a successor. But lots of things that are expected haven't happened recently!

https://www.gov.uk/government/publications/cabinet-manual