Yes, I strongly believe that boundaries which are too firm can do more harm than good. I mean, some clients really need very rigid boundaries, and with them I think this would work but the purpose would always be to move toward healthy AND flexible boundaries on both sides. It made a lot of sense to me when I was studying gestalt theory and therapy in my final year as a psychology undergrad and they associated disorder with both loose AND rigid boundaries. It's important to both leave out what's toxic AND allow in what's good for you, and failing at either makes the boundary partly unhealthy, I think. I would also add that context is important - therapists normally want to help clients be aware of their needs and find ways to fulfill them while also taking into account the environment, other people, and consequences. I think keeping firm but flexible boundaries in the therapeutic relationship is a great way of modeling that kind of healthy behavior.

As an anecdote, I once read a therapist's blog where she talked about working from home and informing clients they were not allowed to go to the bathroom because that would give out too much personal information about her and ruin the transference. As someone with a nervous bladder, my first reaction was that I would never go to such a therapist, and as a therapist my reaction was to think that this was that therapist's issue rather than something which might actually affect the therapy.