Maffetone does not talk about cycling much at all but everything related to running should apply the same to cycling. But there could be some nuanced differences. He did train Mark Allen the triathlete. Mark wrote some books on this too.
The biggest difference is runners and triathletes fall apart quickly with too much duration + intensity. So there becomes no choice. Cyclists don’t have this problem usually but can still reap the same benefits. Is it possible AeT is different running and cycling.
If someone is motivated enough to read this, they might find the answers.
https://www.researchgate.net/publication/24205037_Physiological_Differences_Between_Cycling_and_Running
I do see by reading the conclusion they point out that ventilatory thresholds can change based on different stimulus and time lines for cycling or running as well as VO2max being sport specific. This would indicate their is potential that cycling AeT is different than running and additional reading that AeT might increase faster for cyclists. Hence if you have been cycling a while then it could be above this 65% Maffetone limit. I would still use Mafftetone as the start point, see improvement and experiment.