Swivel, basically, helps you put the light where you want it, whether the convenient bouncing surface is a ceiling or a wall or whatever your desired framing.
It doesn't necessarily take a 'swivel flash' to do the job you may like: the important factors are, 'Are the flash's head and sensor both pointing where you need them to be flashing, bouncing, and reading?' Tilt and swivel heads make this convenient with a flash shoe, but sometimes bracketry or freehand flash placement can do the same.
I, for one, haven't owned a swivel flash unit since I was like eighteen, ... Rented some, occasionally, when they were on brackets, but sometimes the feature is overrated, is all.
It's worthwhile to have, but the most important thing is really to be conscious of where you're placing the light. (And what any sensors are seeing: those sensors are trying to be your friend, but they aren't telepathic.
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