First, PLEASE provide a link to the post that you refer to. I believe the following is the post that you refer to:
“Key to Calming the Mind – The Five Hindrances”
“1) I have seen this claim that Thina middha goes away at Sotapanna only from you so far. Do you have a source or some more information on it?”
You have not seen it discussed like that because most people do not know enough Dhamma to realize that. There may not be a Tipitaka reference for each and every issue. There are some things we can deduce based on other related evidence.
“2) Even a Sotapanna must have some laziness or drowsiness, right?”
– Your question is based on the assumption that thina middha means laziness/drowsiness. That is not so. Please read #9 in the post in question.
I will try to expand on the above post to provide more info, probably after I finish the next planned post.