<< I believe this is a bug in the operating system. >>
More likely a dispute over DisplayPort 1.2 versus 1.4, or a bug in the response from the display.
to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.
This query is only sent at certain times:
• at startup
• at wake from sleep — so momentarily sleeping and waking your Mac may work
• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go
• on invoking Option-(Detect Display) button in Displays preferences (from another display)
>> So it is the DISPLAY that tells the Mac what its capabilities are.
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In the case of DisplayPort 1.4, this includes data compression, and we have seen a few reports here of displays that report lower capabilities when set to DisplayPort 1.4 (likely because they don't have the compute-power in the display to handle the de-compression at full display speeds.).
The recommendation is to experiment with On-Screen-Display settings, and see if DisplayPort 1.2 gives better refresh rates, since the display does not have to do any decompression on the fly.