From the announcement post:

12 of Retro Classix games (titles developed by Data East and re-published by Ziggurat Interactive) are going to be delisted on April 30th, 2024. The silver lining here is that each of them are discounted -50% until the time of the delisting – here's a link to find them all: https://www.gog.com/promo/retro_classix

And here's a list of the titles:

BAD DUDES VS DRAGONNINJA
Break Thru
Express Raider
Gate of Doom
Heavy Barrel
Joe and Mac: Caveman Ninja
Joe and Mac Returns
Night Slashers
Super Real Darwin
Super Burger Time
Two Crude Dudes
Wizard Fire

Also, all games are sold as emulated arcade titles.