A few years old but British Cycling recommend protein intake during exercise if you are doing fasted rides for fat adaptation.
“If you are fully fasted, as well as being low on carbohydrates, you are also in a nitrogen/amino acid depleted state. This potentially could have a negative impact on recovery from the ride. So, if you take protein on during these rides, can you still get the fat adaptation benefits of riding completely fasted without compromising your recovery? The answer appears to be yes so, during these rides it is a good idea to sip on a protein drink”.
No idea if this conforms to current science.
FWIW I’ll bet anyone a billion pounds/dollars/euros that for a short workout that fits between meals protein is not necessary or beneficial but if your ride crosses a meal time in which you would normally ingest protein then it would help.