The ICANN Registry Agreement[1] sets the rules and regulations that a Registry has to abide by in order to be able to apply for the rights to a TLD. Section 2.10(c) states that the Registry must charge a renewal price that is the same as they charge every other domain registration on the same TLD. Meaning that they can't suddenly decide your domain is premium after you've already registered it. The renewal price must always be the normal common price.
But, further down the section you'll see that
>"2.10(c) shall not apply for..."
>"The parties acknowledge that the purpose of this Section 2.10(c) is to prohibit abusive and/or discriminatory Renewal Pricing practices imposed by Registry Operator without the written consent of the applicable registrant at the time of the initial registration of the domain and this Section 2.10(c) will be interpreted broadly to prohibit such practices."
[1]https://newgtlds.icann.org/sites/default/files/agreements/ag...
In summary, the point of this section is so that unless you explicitly agree to it in written statement, Registries cannot change your domain status from non-premium to premium after you've already had it registered as non-premium.
However, Registries have bypassed this section by (speculation here) requiring Registrars to have Registrants waive these rights granted by ICANN, otherwise Registries simply deny access to their TLD.
I believe all of the Registrars have this hidden somewhere in their agreements last I checked. Here's Cloudflare as an example. Their Domain Registration Agreement[2] Section 8.6. You agree to waive section 2.10(c) by allowing variable and non-uniform renewal pricing.
[2]https://www.cloudflare.com/domain-registration-agreement/
Same thing with GoDaddy[3] section 2.10.
[3]: https://www.godaddy.com/legal/agreements/domain-name-registr...
Same thing with Namecheap[4] section 11, second sentence.
[4]: https://www.namecheap.com/legal/domains/registration-agreeme...
Same thing with Porkbun[5] under Terms of Service, first paragraph.
[5]: https://porkbun.com/legal/agreement/domain_name_registration...
Even more interesting is that GDRP[6] defines this as forced consent and not legal.