Hi,
I defer. The pool house would be designed for structural settlement of 25mm or so; however, the pool itself would be designed for zero settlement - remember, the water in the pool is replacing the soil, and hence the foundations under the pool are likely to be under stressed. Thus it is unwise to connect the two in the first instance.
Having said this, I am a bit sceptical on the mitigation of liquefaction potential by increasing the width of foundation (that is combining the two?) is a good idea or not. In this scenario, I would recommend to improve the foundation soil first to minimise the scope of liquefaction.
Rgds