Enamel paints don't play nicely with HaT's new plastic, and the official word from HaT is use only acrylic paint. But Humbrol do make acrylics in many of the same colours as their enamel range, I'm sure that's what the guys are referring to.
Yea I have found that with the new soft plastic (that chunky blue stuff) the enamel paint sometimes needs to be re coated. With the older HaT figs (the grey plastic) it works really well.
I use the oxford blue for my pruskies just to give a different appearance.