I agree with those posters who say ignore everyone who says this is them gearing up to get rid of you.
You’ve mentioned many things which were positive and which indicate they expect you to continue in your post. It’s typical of the anxious over thinker (your phrase) that you are finding it hard to give the positives their full weight.
I think the two points this manager tried to raise were made poorly, as it is hard to figure out what actions and behaviours of yours he was really talking about.
You can ask him for a follow-up conversation to help you understand the feedback you received at the performance review. Remember though he may worry he got himself onto thin ice and that you may be preparing to complain.
If you have this conversation make sure you are highly professional - repeat the two points he made and say that you would like him to give you concrete examples of the behaviours that he thinks need to change. Emphasise this is because you want to be able to take the feedback on board and address it. Try to strike a diplomatic balance - don’t make it his fault for not explaining but don’t take the blame on yourself for not understanding.
If I was to read between the lines and guess. The tipping too much towards home life is likely to be what various posters suggest. I’d add: Are you by any chance underestimating the stress that others in the team are under who are not the parents of young children? When you are rushed do you make comments connecting the pressure you are feeling to you being a parent of a young child? As an “anxious over-thinker” did you used to work long hours to do the work in a way that made you comfortable, and you are having trouble adjusting to the constraints you now face?
You are adamant that you don’t talk about DD - firstly, in some workplaces the tolerance for women speaking about their children, childcare and so on is still unbelievably low, secondly, some people think they aren’t talking about their child or making references to their role as a parent but colleagues experience it quite differently.
The comment about robust is not unclear, it’s just not possible to tell from the post and your answers whether it’s fair or not.
I think I would ask yourself whether this manager is not great at managing a returner, or whether there is some truth in what he tried to say. I’d also ask myself whether some of what he said could have come from comments from others in the team, whether fair or unfair, and if so, what and why?
It sounds to me like they rate you, and as someone else said, they think it’s six months in and they want you to have fully adjusted to your new reality.
One hard nosed piece of advice. Always blank every comment and question that might be trying to sound you out about whether you are going to have another child soon (and go on mat leave again). Graciously respond to assurances that they see you as part of the great future of the team “that’s brilliant, thanks, I love being part of this team.”