I think that I know the reason for it luckily. Because at that time my late American husband/teacher also pointed out the same error to me, he must fail to suffer my misspelling--ture any more. (I know that there are a lot of other mistakes in my emails to him. Thank him to encourage and allow me to write in poor English boldly so much. )
I must say that I was rather shocked when I realized my mistake at first. It is so natural for me to spell "ture". It is all due to its pronunciation. It seems the subconscious of most of Chinese is the same. "True" looks a little heavy-headed. If we change it into "ture", it looks so balanced. In English syntax, it is important to seek the balance of sentence, in order to avoid the heavy head, people use "it" to replace the real long subject. Similarly in Chinese calligraphy, it is also important to seek the beauty of balance.
I have learned a lot from my cross-country and cross-race marriage. I feel our human nature is the same, but our biggest difference lies in the attention to detail. Oh, if at that time we both knew about our different details, maybe such kind of huge tragedy couldn't happen.