Well, massclaim seems to hardly ever work out in this setup even when you do it later when more information is available. Doesn't sound like a good idea to me.
So the big benefits to me for mass claiming early (not necessarily mass claiming in general later as that is a separate issue) are:
1. force mafia into making a decision early on about what they should claim. This pigeon-holes them into a role that they can't escape from. If they claim a PR they are stuck with that for the rest of the game and the setup or later night results may /out them in their lie.
2. it can cause the pool of potential mafia suspects to be shrunk. Right now, if everyone that is town removes themselves from the pool we are looking for 3 mafia in 11 players. claiming will generally create two separate pools (1 for PRs and 1 for VTs). Within the PR pool there will often be confirmed town players (Masons for example or the UB) and often ends up looking something like--depending on what the mafia fake claim, which of course we don't know what they will do (1 mafia out of 3) for the VTs it can end up looking something more like looking for 2 mafia out of 7. This numbers can go up and down and sometimes aren't any better but there are scenarios where the lynch pool is reduced to help the lynches be more likely to be correct
Of course there are downsides, PRs being outed without using their role. Really this only applies to cops (and to a lesser extent docs) because cops are the only PRs that require their night action to be disclosed at the start of the next day. So a Vig or RB (1-shots especially) can still use their roles at night (of course this doesn't account for the potential of mafia having a roleblocker.
So basically I think the idea isn't to figure out which setup we are in. But to instead shrink the lynch pool down to a reasonable size which is a boon especially on the early days. In my opinion giving up a PR for a mafia lynch day1 is a worthwhile trade, which while not guaranteed (on both ends) would be the goal and risk.