Wrong thinking?

Yes. While computers are often used for this trading, the computers are programmed pretty well, because if they weren't, they would be constantly losing money for their owners/operators. So, you will rarely see "the computer" snap up large asks, because that is a very bad option trading technique. Instead the computer would break it down into smaller trades, and see if it could collect the number of contracts it wants at LOWER ask prices. Heck, that's what I do when I want to buy a bunch of contracts (rarely, because I usually sell contracts).

If you look at yesterday's bids and trades you still don't know what would have happened if I had tried to sell 100 contracts Jun 450.

Well, we do know that when the $5.15 trade took place, there were 58 contracts on the ask at $5.20. And we also know that only 4 contracts traded at $5.15. So we KNOW FOR SURE that the person(s) (or computer(s), whatever) that wanted to sell 58 contracts at $5.20 only managed to sell 4 of them at $5.15. What we do not know is if you put an ask in for 100 contracts at that time for let's say $5 what would have happened. Maybe all 100 would have sold, or maybe only 6 would have sold. Probably only 6 would have sold because that's how many sold at $5 or higher throughout the entire day of trading. But you never know, maybe at that instant suddenly someone would pop up and agree to an ask of $5 for 100 contracts. Not likely though.