What do you mean by «actual full-on "this is a computer used for x purpose"-level encryption» ?
Both iOS and Android use hardware full disk encryption and RAM encryption.
Keys for all files are in RAM, keys for RAM are in Secure Processor, so you can’t dump data from RAM chips via direct electrical connection and see keys for files.
I think this answers my question, in that I wasn't sure if the encryption methods used by modern phones is sub-par compared to other computing devices like laptops or servers.
At least based on yours and sibling comments, the title "modern phone encryption kind of sucks" is really more that encryption on modern hardware in general is somewhat fallible, and that phones are just the canary in the coalmine that demonstrates it.
Both iOS and Android use hardware full disk encryption and RAM encryption.
Keys for all files are in RAM, keys for RAM are in Secure Processor, so you can’t dump data from RAM chips via direct electrical connection and see keys for files.