Since this flex whip is supplied as an integral part of the cooktop (instead of being building wiring), and consists of what I presume are fixture-type wires in a length of FMC, the conductor-paralleling provisions in 310.10(H)(1) may not apply -- UL is the one who makes the decision on whether wires in an appliance can be paralleled or not. Furthermore, the paired wires may go to different modules in the cooktop -- it appears to be common for large electric or induction cooktops to be broken up into multiple parts for load distribution purposes.
However, there is precedent in the NEC for treating the stove wires as tap conductors from the branch circuit, as per 210.19(A)(3) Exception 1:
Exception No.1: Conductors tapped from a 50-ampere branch circuit supplying
electric ranges, wall-mounted electric ovens, and counter-mounted electric
cooking units shall have an ampacity of not less than 20 amperes and shall be
sufficient for the load to be served. These tap conductors include any
conductors that are a part of the leads supplied with the appliance that are
smaller than the branch-circuit conductors. The taps shall not be longer
than necessary for servicing the appliance.
In that case, they cannot actually be paralleled; I would suspect that they lead to different parts of the cooktop, even, as I mentioned above.
For box fill purposes -- I personally would count it as four conductors, even though only two current-carrying terminations are provided by the appliance manufacturer. It isn't five, though, because only the largest EGC counts for box fill purposes as per 314.16(B)(5).