A TS is a CB, but a CB is not necessarily a TS. The WX radar detects precipitation intensity, so a red cell can be whatever.
To fly through a red cell is not very unusual. BOM in the monsoon season has a CB/TS on final to runway 27 nearly all the time. Everybody flies through it.
It’s about reading the whole wx picture. Cloud tops? Lightning? Just rain? What do you do if the radar shows red from from one end to the other?
I have once flown through a micro burst. Not fun. In that case the wx radar showed green/yellow with some small red dots. No real red flags, but there it was. Massive rain, so hard we could barely hear each other. The aircraft kept flying. Just.
I’m amazed the engines kept working, but I’m still here.