As a trainer, I agree with that statement as a general principle. However, one also needs to consider confirmation bias (the tendency for people to see what they want to see).
And that's the problem. Fanfare a *big* improvement, and people will be disappointed if it's hidden in the small print that it's not all that it seems.
You maybe know that the it's not 100% HSTs on the line, but will every one, who is only an occasional traveller, or not have an interest in trains? That I doubt. And without seeing the question, a reply should remove any ambiguity.
Let's put the same message conveyed in the tweet into a different context: "Emirates operates A380s on routes to London, Paris and New York". Tomorrow they have a Boeing 773 operating the LHR-DXB route - does that make the original statement untrue or misleading? Does the person who saw that and booked the flight on the assumption that it would be an A380 have any grounds to complain? I say no to both.
Again, it's the small print that's the issue.
ScotRail Twitter have a long history of trumpeting the good things, but long shy away from anything that's not so good.