Not weird or YMMV, just a totally different situation. It is pretty much SOP to allow changes on same routing within 24 hours of ticketing. There needs to be the same inventory on the changed flights in order not to incur additional charges. This 24 hour policy does NOT apply to refunds/cancellations.
Oops I booked the wrong date... Oops I booked the wrong time... no problem correcting within 24 hours of ticketing.