Why is it you have to posit that piece of crap, rather than assuming I think that the underlying circumstances should be the same as a basis for appliction of a prior decision as precedent? You don't seem to want any restrictions on what Congress can do.
The underlying circumstances* in the two cases were the same. YOU chose to ignore that and focused on the type of commerce being regulated. Since the type of commerce was different, you opened your yap and embarrassed yourself.
* From The Shreveport Rate Cases, 1914:
"It is for Congress to supply the needed correction where the relation between intrastate and interstate rates presents the evil to be corrected, and this it may do completely, by reason of its control over the interstate carrier in all matters having such a close and substantial relation to interstate commerce that it is necessary or appropriate to exercise the control for the effective government of that commerce."
Controlling an intrastate activity that is related to interstate commerce is the underlying circumstance.