A good manager would still make clear that their hands are tied and this is all they can offer at this time. They will have to check with upper mgmt for any further options depending on the response to their current offer.

There are a million legal/safe ways to say that the negotiation is not over just keep pushing.

It could also hint that the manager thought the commenter was one of those social cripples that cannot handle negotiations professionally but it doesn't sound to be the case.

Out of the million safe ways to say the negotiation is not over, quite a lot are so obscure that most employees would not even pick up on the subleties. (And if we're honest, we all know coworkers who wouldn't get that hint even if the manager outright told them their hands were tied at this point in the negotiation)

Without blaming the manager for the decisions of those above them, surely you have to see that this strengthens the argument that you shouldn't trust this person?

Maybe - I'm mainly making the point for future situations where it may make sense to stay if you don't adopt a binary trust mentality (which upper management probably does not have).