I created two pages based on the "new editing experience".
Pages created with this option seems to have a bit of different styling compared to pages formerly created - which is ok.
Now while inserting one page into another by using the standard 'page include' macro, the included page has a different style (eg. table heading colors are different, font-size is different). Left column is the included page:

While viewing the included page standalone, new styles are adapted (which is what I expected)!
Also interesting, while editting the page, the live macro view of the included page is using the the new styling:
Once I publish the page however the styling is changed again!