To me personally, that would make sense if you either:
1. are trying to reduce the cost a purchase price
2. preferring a rounded edge device, versus square
The 11 Pro Max 256gb is $1149.99 from a carrier and no longer available on the Apple website. The 12 Pro Max 256gb is $1199. You would only be saving $50 unless buying it used. If you want an 11 Pro Max 64gb, then that one is $999.99. If you buy the the 12 Pro Max 128gb it would be $100 more. I think the 12 Pro Max is the better choice with the upgrades and new design. But, if you want to save money and can find a used 11 PM for a good price, that would be good too. The battery life on the 11 PM is the best.
Just ordered the 11 pro max 256 due to Verizon offering it for free if I traded in my XR and switched from T-Mobile. Family wanted to switch to Verizon anyway and this was the cherry on top. I wanted the extra battery life too