This kind of playfulness ididitmyway refers to could also be considered "coy", which is flirtatious and does not belong in the therapy room. Ts read bout Winnecot in grad school and this is not the playfulness he refers to.

I've had a somewhat similar experience where I'm saying something that I knew sounds goofy and I can see my pdoc try to hold back a smile/laugh. Depending on what it is I'll say "it's ok you can laugh I know this sounds weird" or "what?". If I ask "what?" he always answers me along with some kind of apology, even if it's casual. I think this is what most people would do even outside the therapy room unless they're being deliberately coy or they're messing with you on some kind of power trip.