Years ago somebody, for the life of me I can't remember who or where, came up with the suggestion that
LvR caught only a fleeting glimpse of Ball's SE5 as it flew into the cloud. A three-quarter rear view of an SE5 (with half of the machine hidden by cloud) DOES look a bit like a triplane layout.
However, if LvR is to be believed, he'd actually been behind Ball long enough to pumps bullets into him and shoot him down; there's no way that an SE5 could be mistaken for a Triplane in those circumstances.
Other suggestions include an attack of vertigo and being struck on the head by the Lewis gun (or a drum of ammunition) while attempting to reload the gun.
If Albert did die in the arms of a French maiden, good luck to him - he hated the job he was doing and I can think of a dozen worse ways to go.
VBR Graeme