but there are other particles that don’t slow down as much and end up moving faster than light

But if they say that light is fastest in vacuum, slower elsewhere, why can they then say that other energy variants would move faster? They'd still be objectively slower than light in vacuum. This is like saying my bicycle is faster than a Ferrari if the latter is stuck in mud or a pit.

Edit: Just noticed that others such as u/nuccy also pointed that out. Agreed. The title is wrong.