By default, 3.6.3 is installed right now. That is more recent than 3.6.2.
I’m trying to pin it to 3.6.2 now; however, it seems to install 3.6.3 on me. I believe I am following the syntax so I’d expect the correct subversion, but I am not as well versed with R and Binder to come up with what I missing here.
UPDATE: I don’t think I’m missing something. I think the packages installed will be tied the MRAN snapshot date I specify but that the patch release version of R cannot right not be specified beyond 3.6. In other words no specific subversions of R beyond 3.5, 3.6 or 3.7, etc. See here. And even that I’m not 100% sure since I haven’t tested 3.5 recently because you said 3.6 is good.