After some research that doesn't seem entirely accurate. First of all the G-05 coolant contains borates and nitrites which the G12++/G13 do not. Also, the G-05 has an acidic pH while the G12++/G13 has a basic pH. The best non-VW branded coolants would be Glysantin G40, Pentofrost ++, Pentofrost E, or the Ravenol equivalents. They are all basically BASF Glysantin G40.
I haven't read anywhere that OAT or HOAT coolants contains borates or nitrates,. It's possible, but my take was that one of the points of going to OAT/HOAT coolants was to get away from those additives. If any coolant brand claims to use OAT/HOAT additive technology then it's PH should be more acidic, or more accurately less caustic. A PH of 7 is the neutral point on the PH scale and anything less than 7 is considered technically acidic. OAT/HOAT coolant have a slightly less caustic starting point with regards to PH because it stays stable much longer. The old school coolants would turn acidic as they aged so the starting PH level was much higher. A PH of over 8 sounds high for an OAT/HOAT coolant.
Here is a link from Glysantin's website about which of its coolant to use, which adds to the confusion. Notice BASF/Glysatin calls VW coolants Si-OAT.
http://www.glysantin.de/en/application.html
Then on the G40 page Glysantin states Si-OAT the same as HOAT.
http://www.glysantin.de/en/products/g40.html
Both G05 and G40 contain silicates. G13 contains silicates. So what is the silicate content of G05, G40, and G13?
I'll posit that BASF/Glysantin had to market a specific VW/G13 clone for some obscure technical/legal reason and not because of any significant difference in the actual coolant formulation.
This is TDIClub where excessive OCD will kick in. We (myself included) will now go on a mission to sort this out only to discover that there will not be a definitive answer. The more we search for clarity the more things will become opaque. Sort of like what we have done with engine oils for the last 15 years.