I can understand if you are referring to Sky Sports or some other sources like MEN. But it’s BBC.
The sport witness article that you posted is nothing but an article that try to make Ed or our club looks like the bad one here, the same goes to other article beside sport witness who also had been heavily criticised Ed & Glazer just for purpose to sell their story to viewers.
Your article has zero quote from the Sporting perspective that indicates what Sporting wants is 70m euro right now. The only thing quote in that article is that Sporting would accept 65m-70m euro last summer and if the 20m euro bonus from Spurs was reasonable, they would accept it.
However, that doesn’t mean Sporting can’t increase their price to 80m euro. Clubs tend to do this for many different way. One is because the transfer happens in January which the fees could get more expensive and another factor is to push the buyer to rise their offer to get closed to that 70m Euro. It’s common.