I agree with the sentiment overall, but Gerrard and Terry were in teams who could legitimately challenge for trophies. Grealish (Championship trophy aside ) doesn’t have this.
Zaha spent his career at Palace but was convinced to move to Man Utd (before returning). Rooney moved from his boyhood club to Man Utd. Andy Carroll moved from his boyhood club when Liverpool came knocking. Gareth Barry spent however many years at Villa before Man City came in for him.
And so on and so forth. Grealish is much in this latter category, if not moreso, than Gerrard and Terry. Let’s just hope we can persuade him to stay for a while longer.