[1] There are similar concepts in many languages, such as Celtic family name prefixes, French particles, and the German von.
Therefore, tussenvoegsels in Dutch databases are recorded as a separate data field so as to simplify the process of locating it.
In Dutch grammar, the tussenvoegsel in a surname is written with a capital letter only when it starts a sentence or is not preceded by a first name or initial.
Although French family names commonly also use tussenvoegsels, those are frequently contracted into the surname, e.g. turning Le Roc into Leroc, or La Roche into Laroche, and thus explaining the collation preference.
Sometimes a surname of this sort will retain capital letters for each of the component words, such as "DeJong", "VanHerck", or even "VanDerBeek".