A concern about the Arborist Splice

[Brion Toss]

Hi again,
Dan, neither stitching nor whipping will add significant compression to add to the handcuff effect. Whipping might apply more, but even if so, whipping can be chafed away. In any event, both methods provide security through shear strength, not compression.
As for how we know if invisible stitching is intact, you may as well ask how we know if the buried tail of the splice is intact; of course they almost certainly are okay, as they can't be chafed externally, or degraded by UV. That leaves chemical corrosion or grit causing internal chafe, and those can be prevented/watched out for.
Whipping 16-strand might seem more attractive than stitching, as the looseness of the weave gives less "bite" to the stitches. Even so, I find that stitching is neater, chafe-proof, and easier done. You just have to be a bit more careful about it.
The strength of arborist rope might seem needlessly high, but there are a couple of compelling reasons for it: shock loads can easily multiply a person's weight (which could easily approach more like 300lbs at times, what with all the gear that arborists take aloft); and the factor of safety had better be at least 10:1, as arborists typically do not use secondary support lines, so must get their redundancy by other means.
Finally, I think Ron is exactly on in saying that it is a given that the splice will be either stitched or whipped. Or both. And by the way, the stitching will also keep your splices from floating apart in a washing machine...
Fair leads,
Brion Toss