I think the trans person going on dates without disclosing that fact is putting themself in significant danger.
The hardest part of being the parent of a transgender person for me has been learning of the astronomical increase in the risk of violent assault and murder. To put it in some perspective, gay people are at a significantly greater risk of being assaulted or killed than the general public. Transgender people face many times more risk of violent assault or murder than gay people.
I don't think transgender people should date without disclosing that fact. I think they owe it to the person they are dating because it is each person's choice if that's a romantic situation they want to be in or not. But they owe it to their self to not be in that situation that could easily turn violent. Many men (in particular) might become very angry if they feel that they have been "tricked" into being attracted to what they consider a man. I just think that's an incredibly bad idea all around.
Can we agree that is practical advice for dealing with transphobia, but that blaming a trans person for not identifying as trans is akin to blaming a woman for wearing the wrong clothing?