There are lots of reasons to dough in at 104. If you are decocting, it lets you decoct a lot. It lets you fix mash pH before you get to the more important part of the mash. Malt doesn't gelatinize at 104 so you can dough in without stirring and breaking up dough balls. As Charlie Bamforth said on The Sunday Session a few months ago, it is cheap insurance against malt that isn't quite as modified as you think it is (as it will continue to break down beta glucans). It's one things to say "today's modified malts" but how many of you take a sample from your bag of grain and observe the length of the acrospire? I do, and you would be surprised at the variation from bag to bag.
So lots of benefits, admittedly minor, and no downside. I wouldn't recommend it for people doing infusion mashes in coolers, but it is easy on my system and I do it each time.
This whole "today's modified malts dictate that you should always do single infusion" argument is kinda crap isn't it? German brewers have always step mashed and still do today. English brewers have always done single infusion, even hundreds of years ago. If something changed between 1980 and 2010 such that everyone should have been step mashing in 1980 and everyone should be single infusion mashing today, the pros never got that memo. Low temperature rests aren't just about proteolysis (according to Bamforth in the aforementioned interview, proteolysis doesn't happen at appreciable levels in mashing anyway).
So I'm all on board with the theory that proteolysis isn't typically required or desired in mashing but I think that does not imply that there is no reason to dough in at lower temperatures.