Any goat that has a sudden feed change (doesn't matter if it is hay, grain, etc.) and isn't slowly acclimated to that feed can have problems like bloat. Or any goat that is allowed to stuff themselves silly on a feed. They are a lot more delicate than a lot of critters. It is not alfalfa alone that causes the problems, it is owners that don't know how to adjust the item slowly into their diet.
Yes, frothy bloat can result in a dead goat (been there, despite emergency veterinary care. My goat escaped her stall, popped the top off the grain bin, and gorged). But introducing alfalfa will not cause that if introduced correctly.