Two separate issues.
I believe the answer you have received is about H1-B transfer/extensions when switching jobs in context of the H1-B annual cap.
The answer you have NOT received is whether when you transfer H1-B from Employer A => Employer B, you will be eligible for 7th year H1-B extensions based on the fact that your Green Card related Labor Certification was pending for 360 days or more for the position you held with Employer A.
This I believe is a more complex issue and one you should definitely consult a lawyer about. The simple answer according to me is, when you change employers, your old labor certification will become defunct (in the very least) by virtue of Employer A losing interest in pursuing it for you. At this point you will have to start a new process with Employer B, which will have to be 360 days old at the time of your H1-B expiration for you to be eligible for the 7th year extension of the H1-B.
Remember, Labor certification is specific to the position that the employer is offering you in the specific labor market that the position belongs to. Therefore the question of that labor certification being valid across employers doesn't hold merit.
But... ask a lawyer. We are not professionals or experts. These are only our opinions based on amateurish information at best.
Good luck, I will be interested to read what you learn about this, so please post an opinion when you discover the truth.