Actually I knew my form improved and I know my power at all durations had improved. I just knew it wasn't 40 watts at threshold; not because I doubted my coach or was worried, but because after a decade of data things stand out and very recently before I had a full gas effort that wasn't what yesterday indicated. I do get having good legs, etc. etc. but it was enough of an outlier to any historical data that it causes question. FWIW, the real increase was 21 watts at threshold. Something I am very pleased with and reflects some other efforts I could actually sustain in training recently when giving it the gas.

I don't second guess my coach, I was second guessing a device where things could and did go "wrong" for a very particular scenario that I hadn't account for. I'm glad I posted otherwise I wouldn't have learned about SRMs needing a calibration procedure in this scenario do to it not requiring it when swapping "normal" chainrings.