You're comparing apples to oranges.I understand that, but if I tried to upscale to 4k to my 1080p plasma, it won't do it. Why? The answer being is that the player has identified the display as 1080, not 4k.
If your premise is that it is seeing my PJ as 1080p due to an EDID handshake, it would not deliver a 4k signal to it.
I cannot force the Oppo to output a 4k signal to my 1080p display.
You can't send 4K to your 1080p plasma since a 1080p screen cannot display 4K. It doesn't matter whether the source is native 4K or native 1080p. The most your plasma can display is 1080p and it has no provision for accepting a 4K signal. No matter what device you use as a source you will always have to downscale native 4K content to 1080p if you want to send it to a 1080p display. This has nothing to do with HDCP 2.2 or any limitation in the 203, it's because your 1080p plasma can't display a 4K image and has no way of downscaling a 4K signal to 1080p on its own. Your plasma rejects 4K signals.
Your PJ will accept a 4K signal but because it lacks HDCP2.2 the 203 is not allowed to send a native 4K signal from a UHD disc to it. The 203 recognises your PJ as 4K, it just isn't permitted to send a native 4K signal to it from a UHD disc. The copy protection in HDCP 2.2 does not prevent the 203 sending a 4K signal to your PJ if the 4K signal it is sending is upscaled 4K from a 1080p source such as a normal Blu-ray disc or from a SD source such as a DVD. The limitation here is solely the result of the copy protection rules implemented in HDCP2.2. If the 203 did not recognise your PJ as a 4K screen it would not be able to upscale 1080p sources such as normal Blu-rays to 4K and send a 4K signal to the PJ because of the same issue that stops it sending 4K signals to your plasma.
Bottom line: you can't send more than 1080p to a 1080p display, period. You can send 4K to a 4K display but if the display is not HDCP 2.2 compliant you can only send upscaled 4K from lower resolution sources to it and you will have to downscale native 4K from UHD sources to 1080p for that display because of the requirements of HDCP 2.2.