What is your question exactly?

The changeset title correctly explains that we refer to the *official* name, and the changeset source links to UrbisAdm, which is the official reference in the Brussels-Capital Region.

Again, the official name does not include the -laan prefix.  This is confirmed by multiple sources and we explicitely write this the changeset description, because we want to prevent careless mappers to "fix-the-mistake-and-add-the-missing-word".  We have seen this mistake too often.

The wikidata entry is much older than this changeset, it comes from a mapper who copied from the outdated and incorrect former version of OSM data.