I think you misunderstood the situation,if you use

EAD to work for a new employer more than your H1 sponsor,you will lose your H1 status, no matter enter the
country with AP.
In some cases,applicant still get H1 extension even using EAD to work,since the immigration officer who approved the case didn't check his/her status carefully,but if CIS find out the fact in future,their H1 will be revoked immediatly,& there is a gap on their status.