Raced bikes in my yoot'. Developed severe degeneration in my c-spine years later, related to the vertical shock loads from many more years of running. Had a fusion and artificial disks done above and below after sustaining mild cord damage. Rehabbed like crazy and did the strengthening I should have done 30 years earlier. Now I ride in the same aggressive, roadie position I always did, the difference being that it feels a whole lot better.
Rehab was was focused on the deep neck muscles and involve a lot of the same sort of strain produced by riding in the drops. I have trouble believing that this will cause problems in a properly prepared athlete. I have my prejudices, obviously, but I think a year in the gym would cure the great majority of the postural issues people complain of on these boards.