You don't even need to complicate things with time zones - how many URC club fans actually watch the Prem or T14 - and vice versa.
Let's be honest - how many rugby fans actually watch a match as a complete neutral (that isn't a one-off event)?
Just for the sake of interest (or "interest" given that it's 3.00am) - just having a look around the neutral Prem clubs' fan forae, to see how much discussion there has been about today's final.
Bristol - none (obviously, club wasn't neutral for the SF)
Exeter - none, no thread for the SF either
Gloucester - Yep, active thread for SF and same thread is still active for the final
Quins - Yep, 4 posts, no discussion. Threads for each SF, I'm only spotting 1 post during play for each SF - neither discussing play
Newcastle - none, thread for one of the SFs, started the following day
Saints - Yep, "active" thread for the SF and same thread is still active for the final - I'm not spotting any discussion of the actual rugby though
Sale - none (obviously, club wasn't neutral for the SF)
Sarries - Yep, thread for SF is still active, I'm only spotting 2 posts during play of the SFs
I don't blame any of them, they're neutrals watching because of a love of the sport, and the competition in which their club plays.
Only Shedweb had any actual discussion of a SF whilst it was in progress.
These are places that people come every day to talk about rugby, their club, the rest of the league and the sport as a whole. These are the places where the couple of hundred most dedicated rugby fans on the planet hang out and talk about club rugby. I'm sure plenty watched the SFs, but they weren't talking about them.