That discussion is nothing more than a forum post, as much anecdotal as something posted to reddit. Whoever told him the top case had to be replaced is in error; the battery is glued to the top case, but with special adhesive that releases when pulled (like a strip of tape). iFixit calls this a “moderate” on it’s scale of difficulty.
It is glued, but designed to be replaced.



That chassis hasn’t been for sale for 4 years, so judge repairability on what they sell now. And regardless of sourcing it from Apple or not, you can easily source the battery.