Speedup with multi-head Turing Machine
First, the one-move shift is definitely NOT standard, but, as far as I understand, it only strengthens the result in that article. If a machine with the special operation can be simulated, then of course a machine without that operation can as well.
Second, here are some papers by Hans-Jörg Stoß dealing with multi-head machines. No one-move shifts here.

k-Band-Simulation von k-Kopf-Turing-Maschinen (1970) - establishes that $k$-head and $k$-tape can simulate each other without changing computation time.
Zwei-Band Simulation von Turingmaschinen (1971) - simulates a machine with $k$ heads on an $m$-dimensional tape by a machine with 1 normal tape plus 1 stack, establishing a rather precise time bound.
Linear-Time Simulation of Multihead Turing Machines (1989) - linearly simulates a machine with $k$-heads on a $d$-dimensional tape by a machine with $k$ separate $d$-dimensional tapes plus 1 normal tape.

Unfortunately, the first two are, as far as I know, only in German. The full text of the third one (translated) is here: doi.org/10.1016/0890-5401(89)90037-0