Three ancestors, everything else a cross
The cultivated citrus of the world descend largely from the pomelo, the mandarin and the citron, crossed and re-crossed. The bitter orange is pomelo × mandarin. The sweet orange is a variety of the bitter orange. The lemon is a hybrid, and bergamot is a variety of the lemon. Yuzu is a cross of Citrus cavaleriei and mandarin.
Which means most of them have no wild home
A hybrid arose in cultivation. Asking where the lemon is 'from' has no clean answer, and any confident sentence naming a native range for one is describing either a parent species or an industry. TeaHQ carried four such sentences until they were checked.
The names are commercial
Sweet orange is recorded by the USDA taxonomy as Citrus ×aurantium var. sinensis — a variety of the bitter orange, in the Sweet Orange Group. Bergamot is Citrus ×limon var. bergamia. Neither is a species. The trade names are not wrong; they are describing a market rather than a lineage, and both things can be true at once.
What survives the correction
Everything about how they are used. Bergamot’s Calabrian oil, Xinhui’s aged mandarin peel, Korean yuja preserve, the Tunisian orange-flower distillation: all of that is trade and cultural knowledge and none of it depends on the plant being a species.
What to do with this as a reader
Read citrus origin claims with more suspicion than most, and citrus PROCESSING claims — where the peel was aged, where the oil was pressed — as the more informative ones, because those are about a place doing something rather than a plant being from somewhere.