Originally Posted by irishguy28

It's shown in your first post.

You're being offered 24F (for free), or 24E&F (for a fee). You're not being offered 24DEF, so someone is already sitting in 24D.

Either they picked 24D as normal (for free), or they may already have been offered the 3 options; 24D or 24F (for free); 24DE or 24EF (for a fee) or 24DEF (for a greater fee).

I'm not saying this is conclusive proof that they have done it this way - but the system is set up to allow this. You don't know for sure whether the person who selected 24D bought a "free seat beside them" option or not, but it's entirely feasible for them to offer the same deal to a person wanting to sit in 24F.

Now that they are proactively offering such offers, presumably the seat map offering is tweaked to allow at least 1 or 2 rows to be "held back" to allow such offers to be made.