The links you’ve attached is not Brachycephalic Airway Syndrome/soft palate.
This is a stomach and/or same area issue. The dog in the link is trying to pump something out n nothing comes out but foam, gets weak etc...You can tell as the stomach is contracted. Was he checked for BLOATING? If you press on his stomach does he whine? Some won’t either.
Bloat usually comes on very quickly...
Have a swollen stomach
Look at their stomach
Try to vomit, but nothing comes up
Stretch with their front half down and rear end up
Not to scare you but bloating is dangerous. Was he checked for that??
IMO, the dog in the video is reacting to an airway obstruction/narrowing...either elongated soft palate or hypoplastic trachea, or both. The struggle to get air in and out is creating the foam. The foam is adding to the airway blockage. The struggle to breathe increases the heart rate and the demand for more air...(a vicious circle) until the lack of air causes the dog to pass out. Then the dog relaxes and recovers, hopefully.
If your dog is exhibiting these symptoms, it's time for a Veterinary specialist(one that is VERY experienced with Bulldogs) to evaluate for elongated palate and/or narrow trachea.
I also think that treating your dog for stomach related issues is a skatter-gun approach because your Vet is not confident in their diagnosis.