OP you are definitely, definitely not overreacting.
I still think many people in our society and on this thread don’t get safeguarding.
Safeguarding is not about ‘proof’ or conviction. The last thing it is about is evidence. Most abuse is very hard to get evidence, and that is not our job as members of society. Our job is to ‘alert’.
It’s about the greater understanding that we now have that red flags, inappropriate behaviour, inappropriate relationships, worrying signs. These should be acted on by each and every one of us. In fact it is so important that now if a teacher or professional suspects any kind of abuse, they MUST act on it and tell someone. They absolutely do not need proof, there very rarely is. The key word is suspects!
The action is to alert an authority (and if a professional and follow appropriate policy). They have the thresholds to act, and the ability to act.
The whole point is that we as parents or lay people do not have the training or power to make the judgement - so we must pass it onto to others that do. We don’t hide the information ‘just in case we are wrong’. And if we are very unsure, we can call NSPCC or similar who will advise.
This is because most abuse happens in secret and there were terrible cases where so many people ‘suspected’ but did nothing and told no one. Or told others and they did not act. And we as a society woke up.
So OP you are doing what every single one of us is supposed to do.