There is no doubt that some of the double flowers of shrubs offer something quite luxuriant to the eye. However, double flowers are often more difficult for the bees to use to get pollen so to help the bees it is usually best to avoid double flowers.
When I checked out a newly flowering tree at the edge of our garden I was pleased to find it was a beautiful mock orange – philadelphus – but it was thankfully a single flower. What a lovely perfume, too.
Bumble bees sometimes manage where honey bees cannot. Their probiscus is usually longer so they might manage some double flowers or some trumpet shaped flowers due to the extra length. They may be seen later than honey bees – possibly their larger and hairier bodies and the fact that the queens are used to overwintering alone all allowing them to be less worried by the cold.