Brick-on-sand terrace

I've done lots of brick-on-sand paths and seating areas in the past, but we're farming out this project, replacing a small wood deck that has disintegrated over time. Contractor comes by today and says they would like to fill the joints with concrete, not a lot, but some, instead of sweeping sand between the bricks. I've never heard of this. I know you never lay flagstone on sand then mortar it in place, but what about bricks? Contractor swears, through an interpreter, that he's done it this way for years and it's the best way to go. I showed him some work I had done years ago, how stable it is, etc., and they insisted I must have mortared the bricks in place, which absolutely wasn't the case. All done with sand. They want to start tomorrow, so any quick input is appreciated.