Once upon a time, not so long ago ...........
The Royal Marines were in two branches, the Royal Marine Light Infantry, and the Artillery.
In those days, it was might have been correct to refer to "buglers" because they were LI, and LI have buglers.
However, the men with drums in the aforesaid illustrations are definitely drummers, even to the drum badge upper right.
Except for the bass drummer, we can expect all RM drummers in full dress to carry the slung bugle, as part of normal drummer kit.
I think! [My expertise, for what it is, does not extend to the RM].