with gripwalk being the new norm, a lot of last gen bindings are seriously unsafe to ride with newer gripwalk boots. so its not really a surprise that a shop told u that...... blame gripwalk, not the shop techs. they cant legally mount ur shit if the boots/bindings arent compatible. i can promise you that you wouldnt want to ski a boot / binding that doesnt clip in as it should. very dangerous, you'd be ejecting all the time / risking injury
also u kinda sound like the "ski wiz who knows everything" who u despise.
if a shop tech told u ur shit is incompatible, chances are he knows what he's talking about and doesnt want u getting hurt / him getting sued. i highly doubt they were trying to upsell u some boots unless u genuinely needed them in order to mount.
also he's right, true center mounts are fucking stupid 90% of the time.