I doubt you'd cause it any wear or grief by tilling an established veggie plot Chris. I've seen other light-medium rotary hoes get traumatised when they hit rocks or buried rubble in hard ground, especially when they were being used commercially so that happened to them 50 times a day, but compacted clean soil is a walk in the park for that grade of machine. (Solid clay is a much bigger ask, but still rather mild compared with solid, well-consolidated clay that has concrete rubble in it.) In your position, if it were my own garden that I knew had been tilled over to full depth previously, I'd use it. The trap comes when a friend or neighbour wants you to till his back yard that still has the builder's rubble under it, though of course he swears it hasn't. Or much worse, he wants to borrow your machine to do it himself.
My yard has anything from 10cm over concrete rubble, to 20cm over some kind of stone. I can just cut the stone to 4 or 5 cm depth with a wild mattock-stroke, but since it is mostly more than 30 cm thick, realistically it is probably beyond most back-hoes, even with tiger-teeth on the bucket. It's jackhammer country. I'd hate to see your nice classic machine exposed to that kind of thing.
