IIRC Octalink used a slightly smaller dia axle than ISIS…
ISIS was essentially what the US/Canadian side of the cycle industry came up with before HT2 as a bit of a consortium/committee, it’s worth noting the next step, to address the bearing issue was “ISIS Overdrive” basically a bigger (Threaded) BB shell that they wanted frame manufacturers to adopt in place of the BSA format… The best thing about it was the “Open Standard” philosophy manufacturing drawings were published for anyone to use, an open design for use by anyone royalty/licence free…
While the interface was an improvement on square taper, in terms of stiffness and axle strength it was a bit of a bugger to produce in a cost effective way and required some quite fancy forging/swaging tools.
HT2 splines (and the rest of the crank) are pretty simple to produce by comparison, and lighter, hence ISIS pretty much died.