It's actually safer-ish. First: terms. Filtering is good, involves moving slowly through stopped traffic between the cars, usually under 20mph differential.

Splitting is less good, that involves weaving between cars at speed and is actually dangerous.

Some of the worst accidents are rear endings where drivers (not paying attention) just run you over while stopped in traffic.

This is offset by accidents where people do the stuff you're worried about but when it's practiced correctly that's not as big of a risk and generally leads to less catastrophic accidents than rear endings.

It's also just kinda dumb to force a class of vehicle that can get out of traffic jams to instead sit in them