English spelling: where do -tion and -sion come from?

In Issue 135 (Volume 34, Number 3, September 2018) of English Today there was an article by Blasius Achiri-Taboh entitled ‘English spelling: Adding /ʃən/ (or /ʒən/) to base-words and changing from -tion to -sion.’ The author's stated aim was to provide help for deciding the forms of these words and whether -tion or -sion was the correct ending. All the words he cited were ones that can be traced back to Latin or French. That is to say, they are Latinate words that became part of the English language either in a French form as a result of the Norman invasion in the 11th century or later as a modification of a classical form in the Renaissance period. This historical fact was not mentioned in the article. I acknowledge that the purpose of the article was to give guidelines for spelling, particularly perhaps for non-native speakers, and that it might be going too far to suggest that, if you wanted to be able to spell these words correctly, you could learn Latin and maybe French too, but it seemed to me that the author's assertions misrepresented the nature of those English words. I should like therefore to discuss certain points of the article, in the order they were presented.