Why? Plenty of other potential sources for buyers at the bottom; BTL's, downsizers, more couples splitting up and one or both buying a smaller place, increasing uni population means more parents buying cheaper homes for kids for a few years, people buying second homes for weekends or weekday commutes. Amongst others.
Dont forget, the most recent house price increase, over say the previous 5 or so years, took place **as the reduction in FTB's occurred**. One could even use the statistics to 'prove' that a removal of FTBers would increase house prices, as they would seem to be inversely correlated!
So, no removal of the bottom rung, at most a decrease in one source of buyers at the lowest price level, and no correlation of decreasing FTBers with house prices, in fact the reverse.
If you send me your address I'll send you some straw so you can throw it up in the air and grasp at it.