Moot point. For two years I only did any paid work for Save the Children. However I was paid by various country offices around the world. However, if you have a regular monthly or quarterly income from a single source then you are in trouble. That was, just to make life easy, the year they called in my bookkeeping and so on to have a look at. Fortunately I had my contracts and was able to explain that all are different jobs, different places but interconnected so a single organisation worldwide through a number of it national branches and irregular rather than on a regular cycle. I spent quite some time explaining and re-explaining until the centîme dropped.
The problem is made by them because there is no actual single sentence that tells you that, more like it is implied being an AE allows you to earn an income from a number of disconnected sources. However it is generally accepted and is said by them that you have to 'diversify'. In the real world it is nonsense given that if you have four regular clients, three go bankrupt leaving you with none and no new clients with a flat market then you are breaking rules by something beyond your control. So, nonsense it may be, but it is their nonsense and that is what we have to put up with.