The hormones associated with pregnancy etc, act on the colloagen making the ligaments loose and very lax for the very purpose of childbirth. Whihc of course can cause major problems if you already suffer form lax ligaments, HMS or a connective tissue disorder.
I think it's probably due to that fact you've been advised not too risk the ligament supporting your repair area becoming too weak or loose to protect it until it's fully healed.
Hope that helps a litte.
Take care.....Jo
xx