Question about Faber-Castell Spring rate M e-motion

I bought this fountain pen with an M nib. The stroke width depends somewhat on the ink (it works best with Faber-Castell cartridges), but it is closer to 0.7 than 0.5mm. The B nib should therefore be wider than 0.7.
By the way, the fountain pen has worked smoothly and reliably so far, I can only recommend it.