I may be able to clarify this statement on mixing different inks a little better for you.
It refers to 3rd party inks only and not to the mixing with OEM ink, so it is safe
to mix I.S. inks with OEM inks or OCP inks with OEM inks and so forth.
The big no no was only in reference to mixing any 3rd party ink with another
brand of 3rd party ink, Ouch..
When you change over to using your I.S. ink and mix it with OEM ink you may
get a very slight difference in colour (Colour shift) that is all,
both inks will happily work without clogging up the cartridge.
So there is no need to flush (Purge) out any of your cartridges if you don’t wish too,
most guys just fill up and carry on without noticing any difference at all,
if you wish to profile the new ink then wait till you have filled the cartridge at least twice..