I think the claim "that's my biggest contribution to X" is fine, if you feel like that was what you think is the biggest contribution you made to X. Where it s

I think the claim "that's my biggest contribution to X" is fine, if you feel like that was what you think is the biggest contribution you made to X. Where it starts to feel wrong, would be if you somehow started claiming "I suggested it first. It's because of me it's there. You're welcome", when you merely suggested the feature, not implemented or drove it to be implemented.