They have a new type of core on these they refer to as a "low-power efficiency core", which is probably what is enabling these "feats", but as one of the parents to this comment points out we're comparing Windows configured in "Ultra Efficiency" mode to Apple Silicon MacBooks at most configured in Low Power mode...
Anecdotally, comparing to recent (but still older than these) generations of Intel chips I can run my M2 Max MacBook Pro with 78% battery health for longer (without any special considerations) than colleagues running their Windows Intel laptops in Power Saver mode, while performing similar tasks.