Honeymoon first plane changed, award seat went from United Business to Economy

I am going to preface this by saying that I am nowhere near as well-versed as almost everyone here. I am curious about this award booking though.

We booked our honeymoon for this coming summer (as I can't get off work until then). The entire itinerary was booked in business class through UA's website, and this is the only UA segment. The first flight (ORD-YYZ) was on a EJR-170 in United Business (I). The plane was changed (today?) to a RJ-145, which downgraded the seats to United Economy (X).

Almost all of the E+ seats (the highest class on the plane) are blocked off. I assume this is for elite upgrades, which I understand. However, I have the privilege to upgrade my seats to E+ for a fee. The only two available seats are window seats on opposite sides of the plane.

I understand plane changes, and I understand reserving upgrade seats for elite upgrades. However, is it normal to take a booking, bump it down two pricing groups, and then ask me to pay to be one group below where I was originally?

I know United doesn't care that this is our honeymoon, but I thought I managed this pretty well until the plane change.