This idea that seatposts are marked PRIMARILY to protect the frame is not absurd. Hell, in my OP I asked about potential damage to the frame. The reason is simple, a longer seatpost stresses the frame more. Certain frames can take more stress than others, but they just did some math and decided that x is too much force to apply to frames in general, and chose the minimum insertion line based on that.
I'd wager that the distance between the seat and the insertion line is fairly standard as opposed to the distance between the end of the post and the minimum insertion line. If the insertion line is a percentage of the total length, like if 7% needs to be in the bike or something, then that suggests that the minimum insertion line is meant to protect the post. More likely, there is a standard lever arm that the cervelo engineers decided it too large for most bikes and that is why the minimum insertion line is.
This chick at the LBS shop explained a lot of this to me like a year ago but I called her out and thought she was full of it, the frame breaking, really? But honestly it makes sense.
Last edited by LarrySellerz; 02-14-23 at 05:23 PM.