This is a trademark issue-- not copyright. "Likelihood of confusion" on the part of the consumers is the main standard. Seems unlikely a a judge or jury will find that the reasonable consumer will conflate the app and the play.
Well, for one thing the "double up" option is not a part of standard poker. More conspicuously, physical poker involves a high degree of observation/manipulation/etc of human opponents and that is not a part of video poker.
Yes you remove the human element and change some betting rules but at its core video poker is a simulation of physical poker. The parent doesn't have much of a point other than being overly hyperbolic to discount the reality that there is certainly an argument that this was a bug and hack since the exploit sits clearly outside the realm of the game of poker.
Why do you keep ramming Section 8, DoJ, and Congress down our throats? This sort of regulation, if it were to happen, would be done at the state or local level.