Developer mode doesn’t require the proprietary binary.
There are two problems here. One is when the manufacturer sells something with some capabilities and later pulls the rug from under the users and decides to arbitrarily take some features away. This should entitle any customer to take an arbitrary amount of money back from the manufacturer. The second problem is that after a customer buys the product they aren't allowed to own it. If I buy a hammer I'm, allowed to cut it open, dissect everything, modify the handle or the head. That's ownership, not some shallow dismissal that user want to "have their cake and eat it too".
If someone sells you a cake then follows you down the street to take the frosting and one of the layers back, and tells you that any attempt to restore the cake is a crime, you'd start questioning whether it's really your cake to begin with, and what exactly are you eating.
Excellent machines by the way, primarily let down by the proprietary binary Bambu forces users to use for LAN mode which is extremely buggy and slow on Linux, and entirely technically unnecessary.