We just had 3/4" x 3 1/4" red oak floors installed in 2 rooms and our other 2 rooms had the original 3" heart pine sanded and refinished.
They stained all of the floors dark walnut and they look outstanding.

Our questions is whether or not the sealing is sufficient.
They used 1 coat of Harco Superseal 7300 (rolled), then 1 coat of Zinnser Shellac (wax free, rolled), then a top coat of semi gloss Pro Finisher 350voc polyurethane (rolled).

Everything I read says at least 2 coats of polyurethane, usually 3.
Most people say to use 2 semi gloss, and top coat of satin.

I also found that Zinnser's application guide says their shellac is not recommended before a polyurethane top coat.

Is 1 coat of sealer, shellac and poly sufficient?

We are worried that if they do a follow up coat of poly, the sheen will be too glossy (if semi is used) or too flat (if satin is used).
We love the look and feel as it stands, but are worried about durability.

Thanks!

This is just fine. However, more coatings would protect the floor even more.

The installer came back and buffed, vacuumed and applied another Satin coat of oil based poly.
I feel much better now.