I made Proxies in the same aspect as the source footage and premiere pro always assumes that the proxies are 16x9 when connected.
For example I made a test clip with 1920x700 generated a proxy with exactly the same format so 1920x700 my rendered proxy also has 1920x700.
When i connect the proxy inside of premiere it says it is 1920x1080 in the clip properties.
PAR is 1 on both and the proxies are the correct format!