The machine used is very modern. The baseline on arterial waveforms plays tomato roles. It does show direction, however it also shows distal resistance. This waveform has a sharp upstroke, a rapid downstroke and a reversal component. Move the baseline and everyone would say simple tri-phasic. The baseline is below because the distal resistance has changed - post exercise which is a normal part of auto-regulation.
It is a biphasic waveform showing a systolic & diastolic component. the absence of a negative component demonstrates the antiquity of the machine utilized.
I conclude that the waveform is biphasic because of the the sharp rise to peak systolic as well as the sharp decrease to end diastolic with a dichotic notch. I do not believe that it is triphasic because you do not see a flow reversal below the baseline. This waveform is arterial which is the most defining morphology.