That's a fair comment, and a great example of contradiction or ambiguity in the FCOM, where the Task Sharing table clearly shows the two respective actions as simultaneous, as opposed to sequentially in PRO-NOR-SUP-ENG.
On the other hand, the two actions are not interdependent from a technical point of view, and the order in which they are carried out is entirely inconsequential. Whereas the consequences of unnecessarily delaying Engine shutdown is an increased risk factor.
There are lots of procedures where the order they are shown matters, but this isn't one of them.
I'm quite comfortable from an Airmanship point of view, of minimising risk factors when 90% of arrivals are OETA against the rare occasions that shut-down *needs* to be delayed for FEGP to be plugged in.
There is no reason to *wait* for your colleague to switch off the Y ELEC pump before shutting the engine down.
In fact, one has to ask whether it's even relevant when I'd assume that (without any specific guidance) even with the SETWA mod, OET is prohibited when:
- GEN 1 or IDG1 or APU or APU BLEED or APU GEN inoperative.
Or if you're going somewhere that requires ENG 1 shutdown first for either for FEGP to be plugged in, or because of proximity to the Air-Bridge: it's definitely irrelevant because you're not going to be doing the OETA Supplementary Procedure anyway..?
I suppose the scenario is only going to occur if you've decided to SETWA and then the APU subsequently fails to start ! (And of course....that never ever happens 
...)