Unable to bone meal moss blocks with grass ontop

When you bone meal a moss block the moss spreads to the surrounding stone blocks. However, if you want to bone meal the moss block multiple times it will not work as a moss carpet, grass or an azalea bush will spawn on top of it and the moss will not spread with one of these items atop it. It feels as if the moss should still be able to spread to the surrounding stone if the grass is on top of it.