Bookworm permit me to doubt that you have ever been inside a real CB
I think that's the whole point F4F. You talk about a "real CB". Technically a cumulonimbus is a cumulus that has started to glaciate i.e. it has lost its cauliflower-like appearance and started to look wispy at the top, indicating a phase change from water to ice. It doesn't even have to be associated with significant precipitation at that stage. In winter their tops can be really quite low. Take a look at the
Cloud Atlas description.
I have certainly flown clouds of type 3, and I would be amazed if you hadn't, because if they're embedded then you won't tell them apart from the rest of the cloud you're flying through. The radar just shows you precipitation, not CBs as such, and the precip may be very light, none in parts. While (despite the
nimbus) cumulonimbus is not strictly necessary for convective precipitation, most convective precipitation comes from CBs. Can you really tell me that you've not flown through cloud producing convective precipitation?
I've flown through some CBs that I'd rather not have, and I've avoided lots that I was not going to go within many miles of -- what you would rightly call "real CBs". But that avoidance was not on the basis of whether or not they were CBs, but the precipitation, vertical extent etc.
The point I'm making is slightly deeper than scoring a cheap point on a meterological definition. There is a continuous progression from innocent little cumulus to mean SOB thunderstorm. At no point does the cloud put a sign up on its edge saying "Don't fly through me I'm too nasty now".
Instead we all have to build an understanding of the danger signs and the criteria we will use for avoidance need to me more subtle than "is it a CB?".
Please would you confirm what level of pilot's license you hold.
Tell ya what F3G, you start with your qualifications in cloud physics...