Adding page break in Pages for epub file

I’m exploring Pages and pub files and I wonder if anyone can help me with this?
I want to have a page with just a centered text (or it could be an image as well). When I add it in Numbers (using Insert > Page Break), then add the text roughly centered like this:

this is what I get when I open the pub file in the Books app, with the text all the way down the page:

Any tips on making it look centered vertically when viewing in the Books app as well?

I noticed that with images, it’s different. If I add an image and center it horizontally and vertically and stretch it all the way to the top.

So it seems that the issue is with the text only.

I tried to “trick” it by using a text box the same way I used the image, but the issue is that the text stays formatted the way it was inside Pages, and Books treats it like an image so it can’t be selected, highlighted, etc