Whilst the grind path on the SJ isn’t huge, there’s an anti-clumping screen which causes a few grams to get stuck in the chute. Technically you can remove it and brush it out pretty easily but I just purge about a seconds worth so probably 2-3g on the first shot of the day.
I’d imagine it’s slightly more on the x54 as it uses the same flapper thing used on the higher end MK’s. I probably only purge 3G or so on that though.
To be totally honest I’ve gone without the purge before and the difference in taste isn’t really all that noticeable. The simplicity of just having beans in the hopper and hitting the timer button makes up for any retention.