My take on it..

I believe this clearance issue is rooted in 230-9, which requires claerance for open conductors without an overall jacket. The service drop, which is spliced at the service head is typically open conductors, and therefore subject to the clearance requirements. The service entrance conductors, which may be jacketed SE Cable would not be subject ot the clearances due to the overall jacket, and may pass closer to windows etc.
This probably would apply to the meter socket as well, unless local or utility rules prohibit it.