I don't think it is necessarily based on cover, but I have definitely experienced the tree in the most ideal spot being not very conducive to saddle hunting, and this is mostly due to how the trunk branches off at different angles near hunting height. Tough to comfortably get in and hunt trees like that when in a saddle, but not bad when you can set a stand to just sit in. Still doable in a saddle, just not ideal.
But this is exactly why saddle hunting is just one tool in my tool box. Some people seem to feel compelled to try to hunt with one method exclusively. I try to use them all when needed. Saddle, ladder stands, hang-ons, ground blinds, box blinds, ghillie suit in the brush, etc. I try to use whatever is appropriate for the situation. Same goes for climbing method. I use whatever method is appropriate for that hunt and that tree, be it one-sticking, pre-set ladders or sticks, multiple climbing sticks with aiders, etc. Sometimes will still even bust out the old throwback screw in steps. Whatever works to kill those deer is what I try to do.