John, I could never afford a MOF96 40 years ago, but still have some documentation from a wealthier fellow woodworker. The guide bush is given as 11mm - differed from all other Elu guide bushes, which went up in even mm from 10 up.
The kit came with the attachment you show, the guide bush, the dovetail bit, and a cutter depth gauge.
The bit had to protrude exactly 15mm from the base plate. The cutter depth gauge was really just a bent piece of stiff sheet metal, formed into a U-shape, with a bolt and nut going through the base of the U, and a wing nut to secure the bolt, once properly adjusted. This allowed rapid repeat setup, but the first time still needed test cuts.
The dovetail bit used by Elu was also particular: 8mm shank , 14,3mm largest diameter, 13,5mm cutting height, 15 degree angle.
Having said that, I seem to remember trying out my old Hitachi on the attachment (fitted the same guide bush), with a different dovetail bit. Worked fine, just a bit fiddlier in getting the setup right.
The cutting movement was straight in and out - no in one side, out the other was required. which is not to say that it could not be done with a 10mm guide bushing, using the motion you describe.
BTW, there was a thread on the MOF96 here a while back - one of the contributors posted a wealth of info about Elu.