That's interesting, I wonder why now?
Isn't it and I wondered the same.
My OPINION (for that is all it is) is that this is related to warranty claims. Not warranty claims on the Rohloff hubs as such, but warranty claims on high end ebikes, those which incorporate a Rohloff hub.
I know that I have raised this issue before and I'm sorry for sounding like a broken record, but this change to the official guidance, re the amount of oil required in the hub, gives my OPINION traction.
Most of us here are here because we are cyclists who wanted a super reliable, robust, transmission system and the Rohloff fitted the bill. We have learned that it's common knowledge that they leak/mist/weep, this has never been a real issue as bikes are oily things anyway, we are used to getting our hands dirty, a wipe over with a rag now and again wasn't a problem. However, the type of person who buys a Thorn/Rohloff is likely to be very different to the person who buys a (say) upwards of £7,000 Riese & Muller ebike. An ebike with belt drive,Bosch electrics,a Rohloff hub with electronic gear changing plus DISC BRAKES. This sort of bike is a luxury item and tends to be bought by people who wouldn't usually buy a non ebike - I'm sure that we all know them?
The luxury ebike buyer buys from a main dealer and is most likely to have it serviced by that dealer. Their expectations are very different to ours. When they see their expensive ebike dripping oil they don't wipe it over with a rag, it's back to that main dealer and they expect it to be fixed - A warranty claim. A cost to R&M and/or Rohloff. Rohloff have had to address this problem because it's far more of a problem than it would initially appear. The biggest issue on Rohloff ebikes with leaking hubs is that the hub leaks directly onto the disc brake rotor with a fairly obvious outcome - no rear brake. This is exactly what happened to my bike and I know that I'm not alone.
So, we have a luxury ebike, with a gear system that is known to leak and it's known that that leak can create a serious safety issue. Now imagine - Accident - Insurance claim - Engineers report - Lawyers. You get the picture.
I'm not suggesting that Rohloff are recommending anything that would damage their hubs. Rohloff (and us) know that their hubs can run faultlessly with far less than 25ml of oil in them. I can even see a 'service life' being adopted on the hub oil seals (Simmerings) one day, particularly if Rohloff don't get away with this less in/less out strategy.
The bottom line. Companies selling high end ebikes, with Rohloff transmissions, HAVE to address this COMMON KNOWLEDGE issue. These hubs are known to leak oil onto the disc brake rotor hendering the rear brake useless.