This is going to be difficult to write without sounding bias but let's give it a try:
There is definitely man-made rock out there that is more porous than what's available as actual rock. The problem is that people tend to group man-made rock together with what they might have seen from inexperienced hobbyists and/or brand new businesses, or even from what they've seen (Pictures, etc) years ago when man-made rock making had a surge of interest. While man-made rock is still a relatively new
market (In terms of retail) these days there are definitely examples of high quality stuff out there.
The best part is that it isn't just man-made rock from businesses like my own, but also ceramic (Alternative Reef) and even epoxy (
https://www.reef2reef.com/forums/do-yourself-diy/56978-diy-fake-rock-shelf.html).
The idea that man-made rock supports less bacteria than true ocean rock is like a lot of sayings in this hobby... a myth. You'd be surprised just how porous man-made rock can be. As a test to show potential customers just how porous my rock is, I made an inward concave piece of rock and after it was ready, then poured water into it. The water goes right through it, it doesn't puddle. I can't remember if it was GARF, Pacific East, or some other company but an article was written about how deep the bacteria penetrated the man-made rock. The conclusion was that even with dense man-made rock, bacteria finds a way in.. waaaay into the rock. With porous rock it dang near goes all the way through!
With the way bans on rock have been trending over time, it'll be a matter of time before man-made rock becomes a staple in the industry. Over the years the quality has only gotten better, and companies have discovered many new ways to use it. It comes down to communication, information, and popularity. When one of the three increases, the others will eventually do the same. I believe lately it has been catching on.. I'm usually sold out of stock and after speaking to a couple of man-made rock companies it turns out they too are quick to be out of stock as well (Then again I can't imagine a company wanting to say otherwise! ;) )
Hope I didn't sound too bias.. :D