autoapifunction, autoapiclass and autoapimethod do not render returntype in the signature.

[Josverl]

I wish to use autoapi to :

• generate documentation for a set of .pyi stub files
• add manual How To & Why documentation pages using autodoc style directives

I notice that all return types are absent when using autodocstyle directives and specifying autodoc_typehints = "signature"
for the same functions and classes the return types correctly documented by both autodoc and api_docs

Stranger still is that if I set autodoc_typehints = "both", the return type can be shown below the docstring. However I'd much prefer to use the 'signature stlye'

autoapi_autodoc style	autodoc*	autoapi api_docs
autodoc_typehints = "signature"	ditto
autodoc_typehints = "both"	ditto

Notes:
The .pyi has been renamed to .py to enable plain autodoc.
foo and foo_2 are identical

Is this a bug, or am I missing a configuration / value ?
 
Repro can be found : https://github.com/Josverl/repro-autoapi-return-annotation