Admittedly on my Pure Receiver, in comparison to other DAB+ stations, it took slightly longer to decode with blank audio until it started to stream. The other DAB+ stations start off in muffled mono until they properly decode.
Yes, in DAB+ there are two elements, the 'base' stream (which is telephone quality) and then the so called parametric stream which sticks a stereo and HF layer on top. My car radio also starts off with a second or so worth of the base stream, before the audio comes alive.
By the way, most vanilla DAB radios will display DAB+ stations on their display, but produce no audio, had me confused in Sweden a couple of years ago when my DAB only radio gave the impression all the radio stations were silent !
SDL has 6 DAB+ services at present