No, the polyphony should not have any effect on the number of simultaneous MIDI Note events that can be sent when using the keyboard as a controller. Polyphony is strictly related to how many notes can be sounded at once by the keyboard's tone generators, and keyboards are normally designed so that if you try to play more simultaneous notes than the tone generators can handle-- or transmit too many to the keyboard from an external sequencer-- then the operating system will turn off the "oldest" notes as needed in order to free up some tone generators for the new notes. If you're using the keyboard as a controller, you aren't using its tone generators and therefore the polyphony of the keyboard doesn't enter into the picture at all-- although the polyphony of the other device or software that's receiving the keyboard's MIDI will certainly matter.