I am going to say they can... but no.
There are tons of varieties of bricks that are used for pavers. There is no reason to go with your garden variety house brick.
To be clear the OP is talking about something very similar to below - clay cored brick.
Take a good look at this brick - as this is a pretty smooth example. Do you want to walk on that. Note that the corners are usually pretty sharp.
The fact is the brickmakers form these with a rough top and bottom on purpose. That way the mortar binds better and the bricks "lock" into place better.
Notice the core holes too. These are for weeping properties and just to make walls lighter. The edges of these are often sharp too not to mention areas for water to pool and freeze.
And then finally look at the back. The back has grooves in place - you see the 4 notches. All bricks are a bit different but this is normal. So this means there will be more of a gap between the bricks when they are laid out. Giving more chance for freeze heaving and for vegetation to grow.
The reason why is simply - the weeping holes in them provides a weak spot for both water exposure and easier breakage. No matter how you lay these out and flatten them and pour polymeric sand and level it out perfect... Water will still build in the holes. If it freezes it will expand and will crack. Weight from blunt objects will also make it crack easier than its sister, paving brick.
The other thing - who wants to walk on jagged edges? Even with the sand flattened out you will have edges everywhere. Definitely not walking on it with bare feet quickly.
I don't see a reason you would ever use them given the amount of work it takes and you could use another product (that is probably cheaper) that would outperform it and look the same.
As for "these bricks are free"... Yea fine if he wanted to make a little spot to place flowers or something but something this big has a lot of prep before the bricks go down. Why would you spend all that time and effort and then use a crappy finished product. It is like redoing a kitchen and with nice shaker cabinets, nice tile floor, new lighting... then using some left over laminate countertop you had in the basement from another job.