IE/Chrome/Safari/Opera/etc has the expected behavior.
I consider it a bug that FF doesn't actually refresh the fields when you click refresh.
After all, the purpose of the refresh is to dump what you have and reload from the server. For Firefox to then merge any changed information / fields back into the form is unexpected behavior and, IMHO, bad by design.
Also note that this one issue has been fought over at Mozilla for 10 years. It is a source of MANY duplicate bug reports, is considered by many to be a critical failure, and is quite frankly a complete PITA. I don't know how many times I've had to explain to non-techies why the Firefox reload button doesn't, well, reload the page.
Lately I've taken to just telling them that the Firefox reload button is broken and that they have to either hold down the shift key which clicking refresh or use a different browser. Thankfully we have choices.
--- Update due to a comment stating confusion as to what F5 and Ctrl-F5 are --
All browsers (except Firefox) treat F5 as "reload". Which means reload the page either from cache or from the server if cache is disabled. Firefox does do the reload, but it also repopulates any boxes with stuff you've typed in... Provided those fields still exist. IMHO, this is bad behavior as a page may have changed and you end up in a very invalid state with some things filled in and others not.
To be clear, the cache does not contain what you typed in the page; cache only contains what the server sent you. So Firefox itself takes this extra step of trying to merge previously typed in and unsubmitted data. Again, NONE of the other browsers do this and it is a source of much confusion.
All browsers (including Firefox) treat Ctrl F5 as "reload from server". This ignores any files you've cached (images, css, javascript, etc) and pulls it brand new from the server. Thankfully, Firefox does not merge unsubmitted data back into the page when you do a Ctrl-F5.