When I look at offensive stats for the season through 10 games, I have one OL that allowed a sack. My QB's have been sacked way more than that. Is every sack allowed supposed to be assigned to a lineman or are some not necessarily assigned to anyone? Not sure how that works.

It's a bit finicky in the engine. If a blocker attempts to block and completely whiffs then it assigns a missed block/allowed sack (basically the opposite of a pancake). Otherwise if they just engage and eventually a tackle or sack is made due to overall movement it doesn't ding the linemen for that.

yeah basically sometimes the QB gets sacked and its no blockers fault (e.g. someone was unblocked or the QB was outside the pocket for way too long)