They mention that they do standardise some stuff, namely measuring the actual guide number with a light meter with their specified settings and distance here: https://youtu.be/-g_vCijzNdA?t=837
However, just looking at their photos, it's clear that some settings regarding the Ikelite photos are different from the other photos just by looking at the sides of the swimming pool.
I think comparing the f stops between the edges and the centre can be compared within the same image (assuming no post processing was performed), but comparing the brightness between different images will be difficult unless Backscatter can provide the standardised settings.