I wouldn’t expect him to sign it and I don’t think it reflects poorly on him at all. If it was for charity it’d be a different matter.
Roles reversed if a blue who was a cult hero at City played two games for the rags at the end of his career which went virtually completely unnoticed and we heard that he’d refused to sign a piece of rag memorabilia we’d all think he was a proper chap.
A bit of old fashioned churlishness is quite refreshing in the modern world where everybody has to pretend to be nice as fuck to everyone else all the time