The landing performance of commercial aircraft is based on wheel braking, etc; the effect or contribution of aero braking is not quantified and would be difficult to asses - attitude, duration, … , risk of tail strike.
Many aircraft systems use weight on wheels switching - lift dump, reverse, brakes, antiskid.
Aero braking will have a residual lift component which may delay or even prevent wow switching, thus reducing the overall retarding force.
The FAA advice is poorly considered.
Given "the risk of hydroplaning if this appears to be a danger: When confronted with the possibility of hydroplaning,"
If the risk has been identified then avoid the hazard. Commercial operations should have an alternative course of action - diversion, wait for runway to drain.
The risk of hydroplaning after touch down should be low providing there was an adequate prelanding assessment of the conditions. The use of landing performance calculated for a flooded / contaminated runway will provide some alleviation, but never provide assured stopping capability. Check if the performance on a flooded runway takes credit for reverse thrust, also check any assumptions in factored distance, the safety margins might be reduced according to likely exposure, i.e. not the same as everyday operations.