Not op, but that is partially the case. The idea is that in RSA, many of the parameters lie with key-generation. Both in how the private exponent is chosen, and how the primes that form the modulus are chosen. Unless the implementation is totally borked, those choices aren't visible from the key.

Meanwhile with ECC the main choice is which curve to use. This is visible in the public key. Hence, you can just check whether it is a curve that is generally accepted. For picking your private key, you only need a single integer chosen uniformly from a specific range. Whilst that is not totally trivial to do up to cryptographic standards, it is a lot easier than e.g. 'pick a pair of primes at random that meets these requirements.'