On the contrary. What are you trying to validate? That enough people are interested in your product. Anything that gets in the way of that is just another distraction, and there already will be more than enough of those.
> But they were however able to invest in both iOS developers, the required hardware and this tool?
Developer cost is the same. The difference in hardware costs, if there is any, is negligible.
The tool? It starts quite literally at 0$, and the first paid tier is 29$ / month.
There are two cases where I can see how it would make sense to focus on Android.
First, the WhatsApp example: you are making an app that, by its very nature, entirely relies on massive network effects, and somehow can afford to focus on growth without monetising.
Second, a product that targets people with average to low incomes.
Other than that, if you have to pick between the two, I don’t see the point in starting with Android.