Am I overreacting

[Lyra25]

My partner and I had an agreement about our property as to the percentages of equity. For context, I hold more.
we agreed that this would be resigned post marriage to confirm the previous agreement re split still is intended to stand.
I mentioned it a couple of weeks ago and the reply was ‘oh I don’t think those things matter’. I didn’t push it further and mentioned it again at the weekend. The reply that time was you’d be worse off (as he’s since put money in). This is not true as it still amounts to around 90/10 split in my favour and there is mechanism in the original deed to deal with this anyway.
I was upset about this as I felt it was evasive and trying to side step the agreement to re sign it.
he says I’ve interpreted what he said incorrectly but hasn’t provided and alternative meaning other than to say he didn’t say he wouldn’t sign it.
I’m upset on two fronts, firstly the trying to avoid the original agreement but perhaps more so, for trying to deny what he said or what it meant.
AIBU

What was legally agreed and documented
that’s all that’ll matter

If you stay married for a reasonable amount of time, which I presume is the expectation! Won't it be split 50/50 regardless? I know different regions have different rules on this, where are you?

With that attitude off him I’d officially register separation now to make sure your % of property is kept safe!

I would expect it would mean he's 100% committed to the relationship, thinks you are too so it's completely irrelevant.
Like most people don't want prenups, because they don't want to go into marriage thinking it might fail, and think that if you aren't committed, what is the point?