I believe its more of a 'I don't have an investment to keep me going in this path'. If you're starting without an initial investment of EF lenses most folks going to look at the entire field.. currently is more or less equal from a body perspective, but maybe less so from a native mount perspective. Lenses are not cheap, L lenses (which I have some of) are eye watering in cost if you do not make an income from it. Had the R5 not come out I honestly would've jumped. I don't regret buying it, fantastic camera and I could continue with what I invested in Canon and evolve it from there. However, like many things (this includes Nikon, Sony, Fuji and the others) there is room for improvement..
As for going between system A and B and C within a brand.. it does happen. I went Canon SLR to G series back to SLR.. hoped to get weight down, but buy high end all in ones for travel and cost effective under water.. it worked, but you lose stuff with smaller systems (reach, image quality) as you gain other things (weight, cost, etc).
This is simply airing an opinion on what some customers would like to see. Choose to agree or disagree, in the end it is some customers expressing what they think and it is ok.