They did him a favor, and helped him not look like an ass in his file. He'll exist as data for the life of the company, it may as well be neutral data.
Good point. We hear "HR's there for the company's sake, not yours" repeated so often (with good cause), that it's easy to forget that individual actors can still act with above average altruism.
True. My notice wasn't accepted until the 2nd version a few days later. Because of that delay, my leaving date moved to the 2nd February, which meant that I received the company's annual bonus payment as I was still on the books in February.
In some ways, you could say that swearing got me my bonus.
I wouldn't assume they had actually considered that.