i think you need to read what i said again, gerard.
obviously, if you simply slap a set of 650 wheels into a 700c frame the bb drop will not change in that frame, tho the bb height will. however, if you did that the bb height would be so low as to be a problem in riding the thing. my point is that a 650 wheeled frame needs to have less bb drop designed into it from the get-go, in order to place the bb at a suitable height and that design results in observable aspects. in the case of a cervelo, 1.7 cm less. so then, when fitted with wheels, sitting on the ground and in reference to it, the angle of the chainstay on a 650 wheeled P3 is observably different from that of a 700c wheeled one. the 650 wheeled P3's chainstay will be closer to horizontal. if you made a 16 inch wheeled P3 and placed the bb at a suitable height with that frame for riding, the chainstay would slope UP from the axle, to meet it. all i am saying is that an observer, standing alongside these various bikes, can look at them and see these design features fairly easily - can tell if the thing was designed with 16 inch, or 700c wheels in mind - or with a little extra scrutiny 700 vs 650.
obviously, if you simply slap a set of 650 wheels into a 700c frame the bb drop will not change in that frame, tho the bb height will. however, if you did that the bb height would be so low as to be a problem in riding the thing. my point is that a 650 wheeled frame needs to have less bb drop designed into it from the get-go, in order to place the bb at a suitable height and that design results in observable aspects. in the case of a cervelo, 1.7 cm less. so then, when fitted with wheels, sitting on the ground and in reference to it, the angle of the chainstay on a 650 wheeled P3 is observably different from that of a 700c wheeled one. the 650 wheeled P3's chainstay will be closer to horizontal. if you made a 16 inch wheeled P3 and placed the bb at a suitable height with that frame for riding, the chainstay would slope UP from the axle, to meet it. all i am saying is that an observer, standing alongside these various bikes, can look at them and see these design features fairly easily - can tell if the thing was designed with 16 inch, or 700c wheels in mind - or with a little extra scrutiny 700 vs 650.