It used to be an option in Firefox. You have to go dig around bugzilla to find the reasons they removed it - https://bugzilla.mozilla.org/show_bug.cgi?id=1249151 https://bugzilla.mozilla.org/show_bug.cgi?id=606655
...and this: https://bugzilla.mozilla.org/show_bug.cgi?id=570366#c1 "This option isn't supported, last I checked" What a reason. They decided to remove it because it "isn't supported"? So much for "open source" being better at "do what users want"... if you personally don't need that option, fine, don't use it. But don't go taking away things that a lot of others want. I get extremely angry whenever I see discussions…
If the actual backend doesn't support that option, it's indeed a problem that the UI offers it, especially if it's causing a bug. The question if it should be supported is unrelated to that, and not really a topic for that unrelated issue. I've certainly had my own bad experiences with Firefox issues, but that's not a good example.