Probably just an attempt to encourage people to sit down, especially if it is common place most people choose to stand than to sit, which I think is likely on a train 2/3 full at the moment. (I don't know what his experience was like.)
If that persuaded a few people to sit down and consequently made passage through the coaches easier for both customers and himself then I consider it objective achieved.
No harm done so I wouldn't care too much the merits of going through the tunnels and some such. If some people continued to choose to stand I doubt anything will be done.
I’m a little wary of this sort of thing. If he wanted, for whatever reason, people not to clog up the aisles, why not make an honest announcement to that effect? If this doesn’t have the desired effect then simply accept there’s limits as to what can be achieved when having to rely on the actions of others.
The problem with making up stuff is that of cry wolf - when the situation comes where you really properly need people to take notice, they don’t take it seriously.
Having said that, I know one or two people who love a good announcement at certain stations along the lines of “we are now approaching X - there is a joint revenue and police operating taking place there at this time, so please ensure you have your valid ticket ready for inspection, and be aware there may be a slight delay leaving the station if theres’s a queue for the body scanner”. I can well imagine this having an interesting effect when done at the right location!