And you've been wrong for decades.
All the things you write are true, except when you claim that the binaries will automatically be GPL.
The author has to make them GPL, in order to comply with the license, that's true. But they don't magically become GPL if the author refuses.
If the author doesn't comply, Adacore can sue them. They can demand that the author stops distributing non-compliant binaries. They can demand that the author pay them money.
They cannot, for example, redistribute the binaries themselves (against the author's wishes), under the theory that they "should be" GPL.
The court probably wouldn't even order the author to put the binaries under GPL, because specific performance is generally not considered by the courts, when paying damages is a workable alternative.
I wrote the comment because many people don't know the difference between the FSF version and Adacore's Community Version, hence will involuntarily violate the GPL.
I am not wrong. The runtime of the Adacore Community edition is under GPL, as are many libraries included in the Adacore edition that are not included in the FSF edition. Your binaries will be under the GPL. (Technically speaking, you could compile executables with this version of GNAT that are not under GPL by writing your own runtime. Practically, this is pretty much impossible and nobody has ever done it.)
The FSF edition allows you to compile executables without license encumbering, because it is licensed under the mGPL.