> There are many more languages that speak or read (some of) their numbers "backwards", among them Greek, Latin (both directions possible), Celtic languages etc., and of course languages that actually read right to left like Arabic, where our written numbers come from

Ironically, in Arabic numbers are written left to right, just like in the west, reflecting that they were borrowed from India, whose indigenous writing systems are also ltr. It goes to show that not only is there not a "correct" order to express numbers, but the spoken order need not reflect the written order.