People who think LBH is bad at sex and that SQQ does it more than once with him out of pity or guilt have failed to realize that SQQ (SY) is an unreliable narrator.
If SQQ does not want to do something, only death will motivate him, and maybe not even then. He would've rather died than being used as a pawn to hurt LBH.
SY's favorite wife of LBH was the only one not to really have a sex scene, let alone may not have had sex with LBH in the original PIDW.
In those sex scenes, SQQ's actions do not line up with his words. He is easily embarrassed and used to putting up a facade or a wall. He loves the pathetic act and tears LBH puts on.
LBH, by the end, accepted that he can't force people, including SQQ, to stay with him. He lets SQQ go because he loves him and wants him to be happy and to be in the world. SQQ had accepted himself and his feelings towards LBH.
SY has always been in love and weird about LBH. He read a whole novel series he hated the direction of the plot, and all the repetitive story beats because he wanted more LBH. He fell in love with this fictional man before he knew he was.
He always says that the women are pretty and are what any guy would like, but always is more descriptive with how the men look and always how they don't come close to LBH.
SQQ, the character may be older than LBH, but SY is a lot closer in age, with the dead for 5 yrs gap. His mistakes are based on his age, lack of experience, and failure to see the other people around him beyond who they were in the book. When he finally accepts and realizes they are thinking feeling not on script people, do you see a shift in his actions and behavior. He changes into a more authentic version of himself.
We see the action of denying LBH is respected in the extras, much to SQQ's disappointment. It's a game for him in the end. Several times, characters state his actions and words are contradictory and confusing.
All this is to say he likes his sex life. LBH IS inexperienced, and that's realistic, but he does make SQQ happy and does satisfy SQQ. Do you think after months or years every 3 days, he'd still suck at it. SQQ was thrilled at LBH wanting to marry him and is more than willing to try out new things that LBH brings up. SY(SQQ) is a complicated person, but most of all, a weirdo whose narration requires you to look between the lines time after time.
He wondered about what LQG's bullied face would look like. He has a thing for pathetic and capable men. He even stops his assault on SQH(airplane) when he whines and begs/pleads. It's like his thing man.