Nothing in that article suggests that the actual stones come from Europe. It seems like it would be rather impractical to import that much heavy material.

This report [0] from the Historic Districts Council in NYC says:

> Despite the name Belgian block, it remains unclear to what extent, and during what era, paving stones imported from Belgium may have provided the raw materials for New York City’s streets.¹ It is known that the city’s early paving stones included a type of six- inch-square traprock commonly called “Belgian” block, and said to have first been used in Belgium.

>1. While it has often been reported that Belgian blocks were imported to New York as ship ballast, we have not found primary evidence to confirm this practice.

https://hdc.org/wp-content/uploads/2017/08/HDC_Historic-Stre...