yes but there's a huge huge difference between being very near many times and "underachieving" : Rios only played one grand slam semifinal (he went to the final) and didn't lose to an all-time great, it was Korda !
Extending it to "he should have won multiple slams" is completely different from what I said about Borg, Becker and Connors who were very near many years in a row.
OK, and what you personally suggest in case with Becker, for example? Should we count his numerous attempts as almost-titles and put him higher due to this?
Actually I understand what you meant very well. But it can`t work here. Because in the end of the day such very doubtful list turns into... hell, even don`t know what to say exactly.
The same Boris was close plenty of times, but he failed in all of them for a reason too. You can always look at these situations from different angles. You are very near to position "few close attempts" = "deserved to count". It is list of best of the best, attempts should be counted in 10th turn after more important criterias, IMO, and then you realise they don`t change much.