No, you shouldn't be worried. Kids practically train themselves when parents wait until they're ready, with no bribes and no tears or resistance.
It's really quite a developmental stage; they have to have the necessary nervous-system and bladder maturity to notice urges long enough ahead to make it to the potty, and they need to be emotionally / motivationally prepared (parents can help with positive messages, books and videos, puppet make-believe, a set of "big-kid" undies stacked and ready to go…).
And when they are good to go, they'll do it, just like when they were ready to walk and talk. They didn't have to be rewarded for talking. Same for pottying.
Earlier training is almost always long training, and it has more to do with training the parent to get the child to the potty regularly, and to notice his cues between regular trips. Early training often ends up with a frustrated, despairing parent and an annoyed, resistant child. Starting training before the child expresses readiness and interest can actually delay success. Much like pressuring a first-grader to spell correctly can sour him on his ability or desire to write.
You probably know that boys often need more time to achieve the physical/nervous system development needed to succeed with potty training. Be aware that many, many children also succeed in stages: peeing often works first, then pooping, though I've seen reports of those two activities happening in the reverse order. And sometimes night dryness comes much later, especially for boys, so many little guys wear overnighters to bed well into their grade school years.