Naturale is a 'professional use only' product that can be purchased through flooring supply dealers.

Oh that's very unacceptable. If you contracted for Naturale and he switched the product, then he has breached your contract with him and you owe him nothing in most jurisdictions until he provides the product and services that are in the contract. There is no problem applying Naturale over Mega, however the end result may not be the look of untreated wood that you were expecting. The three coats of Mega and the one coat of sealer probably now fills in most of the open graining in the wood. Whether that would overly-compromise the look of just Naturale on the wood is the question you need to answer for yourself. You could, of course, be somewhat reasonable and agree to allow him to apply the Naturale over what he has already done...only with the stipulation that if the end result is unacceptable, then he would be required to start over. However, Naturale is an expensive product...TWICE the price over Mega, so his 'profit' on the job would begin to diminish, but that is his problem, not yours. If this was an intentional switch of product and not a misunderstanding or mistake, then you really have more of an issue here. I wish you the best of luck.

These floors look great and I love the herringbone. Well my floors were coming out looking so good and my contractor’s flooring guy used SEMI GLOSS for the finish even though we all told him not to and to use Satin. Everyone I talked to suggested satin. He said he used semi gloss by accident. So far he only did one coat, can he cover with one coat of Satin and the he’ll be ok? I do not want the shiny floor look. My floors are white oak select so I want the floors to shine through not the gloss.

I would use Loba invisible. Fir will color change regardless. It looks best as natural as possible. Loba invisible will keep it pale and natural for the longest period. One product start to finish. Bona Naturale will need a sealer.