This has got to be a severe bug in the airline's reservation software. If you pull up the seat map shortly after IPO and half the plane has not been selected yet then that entire half of the plane is taken out of inventory for the rest of the week?
No, not the entire half of the plane. You're thinking seats as in the physical things, but airlines treat seats as virtual. On a plane with 150 passenger capacity with 16 first class seats (a pretty normal configuration) you may have, before anybody has booked:
- 35 extra deep discount seats
- 25 deep discount seats
- 25 discounted seats
- 25 award seats
- 25 full fare seats
- 6 instant upgrade first class
- 4 discount first class
- 4 award first class
- 4 full fare first class
Yes, I know it adds up to more than 150 seats, all airlines have more virtual seats to sell than physical seats on all flights so they can overbook a bit. This would be a pretty normal configuration for a not too busy route.
So if you go through a mock booking for a party of five, and you have extra deep discount seats, when you pull up the seat map the aircraft by making a booking you have no intention of completing, five extra deep discount seats are removed from that seat inventory and held for up to 48 hours before being re-released back into inventory. Sometimes, this isn't a problem, but on a real flight, you have 15-20+ levels of discounts available to you, so on average when you take a chunk out of inventory like that, that means that when you go back in you will be kicked to the next level of seats ... at a higher cost. Doing it when booking using miles can clean out the entire section of award seats.
Your physical seat assignment has nothing to do with this, it's a side effect of an FAA regulation where you must have a reserved virtual seat before they can offer you a physical seat, so they all do it this way, even airlines like WN who don't assign physical seats at all have a point at which the seats are removed from inventory before payment is collected.
This is why they offer seat maps independent of the booking system. And, by the way, yes, if you do go and do a bunch of fake bookings to check on things (in the dozens per day), eventually the airline does give you a call and can flag your account to push you to permanently higher fares (it's rare, but it does happen).