I used to dread the beep beep of a traffic update on my RDS-TMC trafficed TomTom, which usually signifies a hold-up, but at least you have been informed and could use other sources to check its veracity. It’s not always accurate as, I presume, the info is dependent on human interaction and they (humans) make mistakes, forget to update etc.
I too was caught in that ■■■■ holdup on the M5 on Friday (I thought an hour would be enough to cover the final 15 miles to base (90% motorway) - someone unfortunately died near J15 so they closed it Southbound) and the last matrix sign before J14 showed the left hand lane open. This gave me hope that the situation was improving but the sign was incorrect, as are many traffic pronouncements.
The TomTom Live “HD Traffic” is much, much better than the free-to-air TMC offering (and yes, I have used both systems rather a lot). The free system only covers Motorways and trunk roads - and even then only significant delays are shown. If you haven’t used HD traffic with a proper truck-oriented satnav, I strongly suggest you give it a go.