I don’t think you can switch the Triumph system off, from memory.
I’ve got it on my Thunderbird. It’s probably not essential for a bike like that, as it doesn’t get ridden in an aggressive way. In fact I don’t think it’s been activated yet.
My view regarding ABS in general is, why not? Okay, it costs a little more but the resale price is correspondingly higher. And it only (potentially) has to work once to be worth the extra.