Agreed it is an avalanche effect, up to a point. From the private key perspective, but not the public key perspective.
The avalanche effect in the context of hash functions refers to the property where a small change in the input data results in a significantly different output (hash value). In other words, even a slight modification to the input should cause a drastic and unpredictable change in the hash output. This is a crucial property for cryptographic for
all kind of hash functions.