You do if you want the brightest scenes to be 1ms persistence too. Like not every scene will be 100 nits in SDR material but the scenes that are you absolutely need around 1600-1700 nits for scenes that reach peak 100 nit if you wanna see them at 1ms MPRT 60hz(1000 nits would be needed for 1.7ms or so).
If you're ok with the brightest scenes/elements of the screen being more blurry then that's another thing but if you want full-range 1ms(as in every scene no matter how bright/dark, no matter what color it's displaying etc. the blur is the exact same) then you need about 1600-1700nits for 60hz.
Unless I'm misunderstanding something(in which case Chief is free to correct me) the brighter the scene/element/pixel on a screen the more nits you need to replicate the same(intended) brightness at a lower MPRT vs darker scenes which would require less brightness.