I've been building snake fan-outs for years and historically there was very little individual pair jacketing other than the foil shield. That was what heat-shrink was for!
Even now with some of the modern individually jacketed snake cables I still heat-shrink as the jacket is so thin and doesn't seem like it would hold up too long.
And the individual jacketed snakes are usually 2ga smaller than the foil wrapped cables.
But the individual jacketed cables are much easier to deal with.
So it is a tradeoff.