Agree this is a very unfair business practice.
But at least for Travel Agents it is clearly stated in the fare rules (ARN-BKK example):
CXR FARE CLASS MARKET TICKET DATE TRAVEL DATE
QR RLR7PXBX ARNBKK 25FEB20 01JUN20
QR PRIME BOOKING CODE R
---------------------------------------------------------------
QR DOH BKK
FLIGHTS BETWEEN DOH AND AREA 3-FAR EAST, AUSTRALIA AND
PACIFIC
REQUIRED K
.