hsts on main port 80, not on other ports

Yes, this is intentional. RFC 6797 states:

     The UA MUST replace the URI scheme with "https" [RFC2818], and

     if the URI contains an explicit port component of "80", then
     the UA MUST convert the port component to be "443", or>>

     if the URI contains an explicit port component that is not
     equal to "80", the port component value MUST be preserved;
     otherwise,

     if the URI does not contain an explicit port component, the UA
     MUST NOT add one.

     NOTE:  These steps ensure that the HSTS Policy applies to HTTP
            over any TCP port of an HSTS Host.

You should run plain HTTP services on a different domain, or even better, use a HTTP+TLS server as a reverse proxy to the internal plain HTTP service.