Managed to clarify with a senior manager on the hotel's (official) interpretation of WoH upgrades wef March 1st.

HGP upgrade for Diamonds:
Without instrument - Deluxe King
Using upgrade cert - Duplex Suite

WoH upgrade for Globalists:
Without instrument - Deluxe King
Using upgrade cert - Duplex Suite

That's right, there is no change in the upgrades accorded. I was informed of the rationale - the hotel considers their Deluxe King room (effectively a junior suite) as a "standard suite" in the context of non-instrument upgrades.

Just a heads up to those "expecting" a non-instrument upgrade to the Duplex Suite.