What games would you consider to fall under the “they ARE BE” umbrella?
Story driven: Hypnosis, The Pill, White Russian, Bloom War, Holstein Girls, Growth Academy (Honoka). I suppose My New Neighbors and Cabin by the Lake would fit as well but they are way too grindy for my taste.
Gameplay driven: Lacto Escape, Irresistible Johnson (RIP), Your Own Living Cowgirl (really old, underdeveloped flash game but I still like it).
These games stand out to me because all of them are breast centric and explore or at least acknowledge the
time aspect of the fetish, remember that BE is just growth in time. Now, if you wanna take it to the next level you add
reaction into the mix, either in the form of dialog, monolog, narration, etc. This deeply enriches the experience as we will know how the characters feel about themselves. To me that's the holy grail of Breast Expansion: Reaction to growth over time. And if the girl just happens to end up with big old tonhongerekoogers, then that's just the icing on the cake.
Also, it's when you strip BE from those 2 aspects when you end up on the usual "has BE" category which plagues this list of games... And comics and doujins and animations and pretty much everything BE related.