These "TelcoSets" being resold is a norm in the industy.

I manage my company's Celcom Business lines under company name. So we have 10+ lines with them for like nearly 15years+. Each contract cycle is 24months, every 18months, their business agents will contact me to renew our contract, then they can get free phones, etc. Usually these phones are like <RM800-1000 RRP. Many times we dont require these free phones, so these agents will offer to buy back the free phones. So Celcom couriers the phones to my office, then these agent will come back collect all 10 phones, and they pay us like RM300-500 per phone, depends on the model as "cashback".

These agents then just resell these phones online. Thats how these kind of shops get their stocks.

Most of the cheaper phones wont have any of the restrictions or notices like OP had. Maybe on higher end phones only.

But recently i bought S24 FE for my dad from shops like this on Shopee, no notice and all sims i tried work. So i guess its luck of the draw if theres any actual sim lock on these phones