Correct. “Dual licensing” means “The conditions in this license OR in that license applies”, not “The conditions in this license AND in that license applies”.
For example:
If you plan on billing a client for this software or claiming it as an expense for your business, this software is provided with source for a one time fee of $50 with future upgrades provided at $25, after which will be under the MIT license. Otherwise this software is provided free of charge under the MIT license.
Also, having contingencies on what someone “plans” to to seems fragile. Suppose I don’t plan to bill a client for this software, nor claiming it as an expense. Therefore, I acquire a copy of this software, licensed only under MIT. Suppose then that I change my mind. I should be completely free to bill clients for the software, since the MIT license freely allows me to do so. Right?
Either I am free to do that, or the software I acquired was not actually licensed under the MIT license at all, but had added conditions. And in the latter case, it was not actually Open Source.
If I am looking to update a site for a client and see software that I need, and the author is asking for $$ for commercial use, and the client is willing to pay, I will respect that.
Presumption of conflict and safeguards against it, or just giving up, has caused a lot of great projects to be abandoned in my opinion.
If you go to github and the source is already there, the source is open. Any definition of open source beyond that is political and legal. And with that source being open, you could just copy it without even reading the license.