The article you are referring to is basically saying - don't connect a Fusion drive to a Mac running an older version of OS X.
This will never change, this is because older versions of OS X do not have the newer software included in them to allow them to 'understand' the newer disk format capabilities used as part of a Fusion formatted drive. This new software is called 'Core Storage'. See https://en.wikipedia.org/wiki/Core_Storage
For a similar reason really old versions of Mac OS X cannot understand FileVault2 encryption because FileVault2 also uses newer Core Storage features.
There is no chance Apple will ever add support for Core Storage to really old versions of OS X, Apple do not add features to discontinued versions of OS X and only provide security fixes for the last couple of versions of OS X which will not help either.
Having a separate older Mac dedicated to running your old applications may be the safest option. You should also seek to replace those older applications or accept the drawbacks of having to as an example dedicate an older Mac to them.
As a comparison I also for my own personal use have some older applications, I use a separate older Mac to run them. I know and realise that eventually this older Mac may die and not be economical to repair or replace with another older Mac. I therefore do not rely on it for anything important.