An experienced traveller, you ought to know that there can be differences between the letter of the law, and how it is applied. Especially as one travels South - and in this respect, as in many, Belgium is a very Latin country.
Tell me about it. I was based in Luxembourg for 7 years and every away landing was abroad, mostly at Sterpenich. Can't remember filing flight plans or using the radio, but then my memory is not very good.
That was before this permit requirement was introduced in an attempt to deter Belgians from registering their microlights in France.
As for Latin countries, if you grow up in Argentina and spend years in Colombia, Ecuador and Peru, you learn things that come in useful in France and Wallonia.