When T increases, and that happens very fast:
serum E2 increases
T changes gene expression inside of all of your cells
Cellular changes occur
Bulk tissue changes occur
Organ systems change
Patterns of though change in your brain
Elevated E2 can counteract changes in the brain and gains can slip away.
All of these changes take time and one's age, genetics are major factors. Other health problems and hormone systems play a major role, think about weakest links.
How long one has had low-T matters a lot.
If you were estrogen dominant before TRT, there is a lot more work required to re-wire you brain.
Global generalizations about these things really do not matter when you are a sample of one. Best thing to do is manage E2, general health/nutrition and make sure that thyroid function is good.