I believe it is a short term band aid to the root cause that causes issues down the line and it's quite expensive to boot.
Fix the actual issue or use conventional methods. Besides this, sealing valleys is probably my biggest pet peeve, most of these roof contractors do both.
With tile roofs it makes the tiles incredibly difficult to lift after.
It makes tile and steel roofs much harder to prep for painting later, if you go rubber coating you are almost sure you are going to need to stick with rubber coating in future.
It doesn't last as claimed.