I've heard that can be a sign, too. 22 months is quite young for a boy (as I understand it) but have a friend whose DS started before 2 and has done really well, now just 2.1 and pretty reliable during the day.
I guess you will be the best judge of whether or not he is able to understand when you tell him that he's going to be wearing pants and using the potty from now on, and to respond when you ask him if he needs the potty. Also, whether he is sufficiently articulate to tell you that he needs to go (am not casting aspersions on your DS, btw - just that DS1 grunted his way to the age of 2 and probably couldn't have told me at 22 months that he needed a wee).
Has he used the potty at all? Is he willing to sit on it for any length of time (I used to read stories to DS1 on it, to keep him on there for more than 10 seconds at a time)? Do you think he understands what it's for? If so, then I don't think it can hurt to try. 'They' say that once you start you shouldn't go back, which could potentially lead to many months of mopping up accidents if it doesn't go well at first. But I have friends who have started quite early, realised it wasn't working and their DC didn't 'get' it, and put them back in nappies for a couple of months before trying again later, successfully. So if you try and it doesn't work, that's always an option.
Good luck with it
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