@Roger_pt , i agree that it's rather frustrating not seeing all the BIOS options that are contained within our machine.
Sadly BCU is not a be all and end all as i've seen options (like 'post mode' and 'post messages') dissapear from the BCU output (though i don't know if this was due to a BCU version change or a BIOS version change or some combination of the two).
As for the difficulty you had with recovering your BIOS settings, 'Replicated setup' within BIOS itself could be usefull for you (after using BCU to set up the hidden options as you desire). You can use 'Replicated setup' to make a BIOS configuration backup to a USB stick and later restore the backup from USB stick should you ever need to reset BIOS defaults. It's simpler than jumping into BIOS, then booting the OS and using BCU to redo your changed. 'RS' is all handled from within BIOS itself (save & recovery that is).
Oddly, i see enable/disable as settings under <Advanced><AMT configuration> within BIOS v1.47 so not sure what option you can't see in 1.51 & 1.53?
<rant begin>
In any case all the above shouldn't matter as it's a simple design choice as to what options HP include and/or expose within BIOS. As such, using thie BIOS tool set, it should be easy for HP to react to their customers needs and make such updates.
Unfortunately, the reality is that despite it's being a simple thing to do (and expose such features directly within the BIOS or indeed update the microcode so we can use the V2 xeon CPU's or even stop puting in whitelists within laptop bios'), HP is anything but reactive to their customers needs (in the way i would like to see).
Guess HP see it as better for their bottom line for customers to spend thousands $$ and simply buy the latest and greatest new fangled machine (even when a simple BIOS update could meet the customers needs). Planned obsolescence at it worst is so much more profitable it seems - though it's at our expense really.
Another way to put it is i find it odd how (lower teir?) motherboard manufacturers can make BIOS updates available on their older boards that include newer CPU's while HP states how difficult it would be to do the same.
If they don't want to do it, make the BIOS tools available and we'd likely do a better job of it.
</rant end>