Wow, I'd never heard that one before (about the taste changing).....I know that a higher estrogen level can cause a dip in supply and make a fussy baby but you've got me on the taste thing.......
I was looking around and couldn't even find this one in the breast-feeding myths, where did you hear it?
Babies' appetites can change on a day to day basis (especially if thier attention is somewhere else - like learning a new skill). Also, over time, babies generally become much faster and more efficient at draining the breast - significantly cutting the amount of time it takes to feed......it's not unusual to be done in under 5 min for an older infant - your little man is around 9 mths? Maybe he's just having a busy day
(if you find some literature on this though, I'd love to know!)