Thanks for the clarification, Ray. Between what you wrote and what I found on wikipedia, it finally clicked - why conflating PAR and PPFD is misleading and causes confusion:
"The irradiance of PAR can be measured in energy units (Watts/m2), which is relevant in energy-balance considerations for photosynthetic organisms........However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the number of photons than the energy contained in the photons. Therefore, plant biologists often quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or the Photosynthetic Photon Flux Density (PPFD)
Yeah, this thread has really helped clarify some things for me as well. Thanks all! The distinction that PAR, itself, is not the measurement is lacking in many sources (or is very subtle and easily missed/confused). This whole thread is a pretty great discussion. I hadn't even considered the watts versus number of photons side of things.