en.wikipedia.org/wiki/Charles_Alexandre_de_Calonne

Calling this a "referendum" is historically wrong.

A referendum is a process in which a measure is submitted to the public/electorate for a direct vote. By contrast, the Assembly of Notables convened by Louis XVI in February 1787 was a carefully selected group of 144 elite figures—princes, bishops, noblemen, magistrates, intendants, provincial representatives, and mayors—summoned to consider Calonne's program.

So Calonne did not have the notables "vote on his referendum"; he sought the backing of a selected advisory assembly, not a popular vote of the electorate.

The article has these two men's national identities backwards.

The Château de Versailles' biography of Turgot identifies him as born in Paris and describes his career in the French state, beginning: "Né en 1727 à Paris...".

Its biography of Jacques Necker explicitly describes him as a "banquier d'origine suisse"—a banker of Swiss origin—who made his fortune in Paris.

So Turgot was not Swiss, and Necker was not simply a French banker; the sentence reverses their backgrounds.

This phrase misstates both the type of tax and its status.

Calonne's 1787 program centered on a general/direct land tax (the subvention territoriale), not on any tax described in the historical literature as a "property added value tax." In Calonne's own address to the Assembly of Notables, he proposed replacing the vingtièmes with "a general land tax covering the whole area of the kingdom" and having taxation administered through provincial assemblies.

It also was not implemented. Standard reference works summarize that Calonne proposed a direct land tax, provincial assemblies, and a stamp tax, but that the Assembly of Notables refused to back his program.

So the article's wording is inaccurate in two ways: it uses the wrong tax label, and it implies implementation when the measure was only proposed and then blocked.

This wording is too narrow. Calonne's famous subvention territoriale was not a tax aimed only at the nobility and clergy; it was intended as a general land tax applying across the kingdom without the old exemptions.

In Calonne's 1787 address to the Assembly of Notables, he explained that the existing vingtièmes would be replaced by "a general land tax covering the whole area of the kingdom" and stressed that "every kind of privilege" would be incompatible with it. The same source adds that church lands would necessarily be included in the assessment. Standard reference works likewise summarize his proposal as a direct land tax plus provincial assemblies and related reforms.

So describing it as a tax merely "on nobles and clergy" understates the core point of the reform: it was supposed to apply broadly, not just to those two orders.