Hi
I am soley dry and have had the same result after a HWE Cc had been in.
A end of tenancy very close to me, I did the clean as some one else had got the carpet. The ladlord turned up and i presented him with a cloth which I had used to get a stain out with my spotter ( after the CC had visited) so I got the job.
The amount of dirt that came out was amazing and I was able to show him a before and after comparison.
So it can happen both ways. But your host guy is correct, do have more faith in the product but don't forgat no one system is 'Jesus in a bottle'
Regards
Martin