Dear Mafan, I read on WP, that in 1918 the then holder of the title of Grand Duke of Tuscany gave up. You say that WP is wrong about this: ok but... could you tell me a sure and official source about this WP error? Thank you very much.
The article that I posted above speaks of Peter Ferdinand who, until 1919 year, was surely an Archduke of Austria an Prince of Hungary.
According to this article Peter Ferdinand, in that year (1919), had renounced to his membership in the imperial house and also to his born-titles as Archduke of Austria, Prince of Hungary etc. in the hands of Republic of Austria.
So you're right if you say that in 1919 none of the people mentioned in the article was the "Grand Duke of Tuscany ": Peter Ferdinand had renounced as the specific title of Grand Duke of Tuscany before, in the 1918 year (WP source), so in 1919 he "was just a Archduke of Austria" and "a Prince of Hungary" into the (former) Austrian Imperial Family.
Remarkable is that, in this article, his mother, Alice (born Bourbon-Parme), was recorded as the widow of the Grand Duke of Tuscany.
Surely Peter Ferdinand, between 1860 and 1918 (approximately), had (I suppose) sometimes protest, against the annexation of the Grand Duchy of Tuscany to the Kingdom of Sardinia and, after, against Kingdom of Italy: but, after the end of 1918 ( the year of his renunciation to dynastic titles as Archduke of Austria and Prince of Hungary), Peter Ferdinand don't make more protests against anything.. .. perhaps, I suppose, because he had already renounced to the title of Grand Duke of Tuscany before, in the 1918 year, in the hands of Emperor of Austria for this particular title: isn't correct?