I take your point on the hydrogen trials.
If EMR were opting for another type of unit for a good portion of their regional fleet, what reasons would management have to avoid mentioning them? They were fairly candid in today's video (e.g. keeping 153s bolted on to PRM stock, arrival dates for various fleets).
The 175/185 units are fairly well regarded, it's not like they have a toxic reputation.
If they were taking on some 156s and then getting rid of their own, I'd wonder why they'd bother doing that (unless they need a short-term uplift in carriage numbers until the known 170s are available).
If they're going to go for 37s and MkIIIs, I could understand them deciding not to crow about it.