Because 1.2.3.4 and 1.02.003.04 both map to the same number.
But 10.20.30.40 and 010.020.030.040 map to different numbers. It's often best to reject IPv4 addresses with leading zeroes to avoid the decimal vs. octal ambiguity.
I don't think .co versus .com is the relevant factor. I can select xampleco by itself, but not as a substring of http//wwwexamplecom. The rules seem so arbitrary and context-dependent that it behaves more like a dice roll than a usable feature.
If a selection to URL feature cares about TLDs, IP addresses, or text beyond the selection range, then it's operating at the wrong abstraction layer. (well, technically Goto foo has a couple lines of code to [bracket] bare IPv6 addresses, but that's not core functionality.)
As an air-breathing land mammal, The Mouse would drown long before reaching implosion depth.