I can't comment on what products are used on the BMW dealerships in your area however when I have done dealership work I have noticed that the quality of materials used were lacking in quality. On the other side of things I did notice this one bmw that I detailed that was still sheeting water long after being purchased. Maybe they had a third party detail the new bmw but I'd like to think that particular dealership had a detail minded Owner
Also several other variables need to be considered like how hot was it that day when the bird pooped? How long was it on the vehicle until it was addressed? also did you have sufficient coverage in terms of your sealant (optiseal, collinite, jetseal)?
Alex, when applying your sealant like opti seal do you spray and wipe down one layer?