Sim, isso é intencional. RFC 6797 declara:
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.
Você deve executar serviços HTTP simples em um domínio diferente ou, melhor ainda, usar um servidor HTTP + TLS como um proxy reverso para o serviço HTTP interno normal.