This should be more directed to Asobo / MS as they typically do not provide manuals for their Aircraft. Most (not all) but most, third party (reputable ones) do. Or, their aircraft are so closely in line with their real world counterpart that the POH’s and checklists, etc available online work without much issue or messing about.
As well, most, provide instructions on how to calibrate throttles, etc, if no full manual was released.
Again, not the case with Asobo planes (or even Asobo partnered planes) such as the ATR.
The CJ4 has a great one, because it was WorkingTitles before it became the default, so there are always exceptions, but it isn’t the rule in my experience.