This method could apply to other tools with the same IPv4/IPv6 behaviour, without further modification. Changing the behaviour in the utility directly would only fix it for that one utility meaning that to fix another you need to do the same work again. It is perhaps also safer than modifying such a core component as SSH: if you introduce a bug the trick can be easily disabled until fixed, if you accidentally break SSH you might cause yourself significantly more hassle.
> This sort of negates that advantage
LD_PRELOAD trickery doesn't negate the advantage of having full source access, patching SSH would also have been a perfectly valid option, but is perhaps a better tool for this particular job.
For another use of the trick see https://github.com/mariusae/trickle (the project looks stale, though that may be because it is properly done and there have been no security/other bugs to fix in recent history) which slips its own functions in the call chain to apply user controlled (rather than firewall/routing level) throughput shaping to utilities that don't offer it out of the box.