Isn't this an issue with a lot of DAWs though? In some DAWs I could have sworn they just deactivate some of the routing when you monitor to prevent this. Mainly asking because I'm trying to keep track of what to avoid in my mixes and most of the stuff earlier in the thread I would run into was fixed throughout 10.6.
Also, doesn't Low Latency mode help one work around this by disabling the plugins that cause that latency?
That depends on the DAW, and it's 'Low Latency Mode' implementation. Cubase doesn't change the routing, but it bypasses latency inducing plugins from monitored input signal chain to minimize latency while maintaining sync. Ableton and REAPER don't change the routing, they offer the ability to disable PDC for monitored inputs to reduce latency. Studio One and AFAIK Pro Tools bypass plugins and further routing. Logic seems to do all three in Low Latency Mode: bypass plugins, bypass routing and disable PDC in some cases, as shown in ansolas' video.
This is perhaps slightly off topic, but regarding to input monitoring the problem with Logic is it does not offer discreet control over PDC while monitoring inputs, and in any case, doesn't properly compensate the monitoring latency to software monitored inputs with or without Low Latency Mode when recording. As shown in ansolas' video, creating the sidechain connection seems to enable PDC on all input monitored tracks without informing the user, or informing that PDC was disabled for monitored inputs in the first place (when in fact it is enabled in the preferences); this should be a global or track preference option, and not depend on the routing.
There are some examples on this thread where sidechain PDC isn't working during normal playback in Logic, even after the fix, and when input monitoring is not involved at all. At least Ableton, Cubase and REAPER are able to handle this correctly: maintain sync during playback and recording with software monitoring, compensate recording positions for monitoring latency, and offer user control over whether to use or constrain PDC or not (or bypass plugins/routing) to reduce monitoring latency.
What I know to be fixed with Logic is that reordering plugins no longer affects sidechain PDC, and sidechain PDC should work between tracks inside same submix or directly routed to master. What (I think still) should be avoided is sidechaining between different 'layers' or 'depths' of tracks/submixes/buses/groups/stacks/etc when different plugin latencies are involved.