The last 2 dealers I worked for (35 years between the two) one used Castrol branded bulk in Castrol labeled trucks, the other used a no name bulk distributor.
I can remember seeing the district factory rep taking oil samples, several times at both dealers.
Never heard any results through the grapevine, I assume no news was good news.
The only time we used oil in containers was when specified in bulletins.
All dealers have to meet "Brand Standards" on several contractual items.
Everything from training, testing, special tools, survey results etc......
Any blanket descriptions of dealers, or the techs, are just wrong.
Just like any trade there are all different types of people, with different talents, and work ethics doing the job.