All of my comments prior were in regards to combining test ester with either HGH or HCG in one syringe. However, you could combine HCG and HGH in one syringe as well although I didn’t think that was what you were interested in doing.
HGH and HCG would share a common stable pH range and I see no issues combining both solutions for an injection.
The comments you read on ExcelMale were regarding Sermorelin not HGH.
https://www.rxlist.com/sermorelin-acetate-drug.htm#description
Again my random internet weirdo opinion is no issue drawing up two phase mixture of test ester and hCG/hGH. Or go full wild and do all three (again being gentle on the proteins during draw).