I have to admit that I find this discussion seems to suggest a difference about nomenclature rather than culture
My British documentation and I suspect John's Australian documentation has nothing to do with America. I don't think there is any British record, either civil or religious that has a box for first name followed with one for 'middle' Indeed the term wasn't apparently coined until the 1830s (and yes that was in America) Before the 19thC few people had more than one forename, the exceptions being royalty and the aristocracy who could perhaps be considered the forerunners.
Just as in your example of Queen Wilhemina, these records have one or more given names followed by a surname. There is no box separating the first from the other forenames. Nevertheless, to give another royal example Prince Charles Arthur Philip George was registered, baptised and married with all his forenames but he is known as Prince Charles; the other names are there but rarely used >Sometimes the first name is not the one predominantly used as in the case of Queen Victoria ( Alexandrina Victoria)
I am having difficulty in seeing how there is any difference between these examples and that of Queen Wilhemina or indeed your Gerrit Jan, or my Helen Mary.
There are cultures that include compound names as 'first' names , France with Marie Therese and Jean Pauls and even dare I say, the English name MaryAnn. It makes perfect sense to put these names together in a first name box.
The 'middle name' box , would perhaps better named as second and subsequent given or forenames. To me it seems less divisive and simpler to use it for those names rather than create differences. .More rules will create more data errors; the suggestions list seems to becoming rather like the work of Sisyphus as it is.
An alternative could be to abolish the box entirely.