I have similar experiences. Everything seemed to happen in the first half year after starting T.
My theory is that it is easier to notice to go from nothing to something, than from something to a little more. For example hair growth. If you have no facial hair, it's easy to notice the first few hairs that happen in the first half a year. Then after those first few hairs, they just sloooowly become more, but that is harder to notice than going from no hairs to some hairs.
I have the hollowing of the cheeks as well, but for me that was due to becoming underweight due to my top surgery infection. I'm curious to see if they remain hollow after I gained some weight back.