Time is a better measure than number of tests. You can't expect a Bangladesh player to have a 30 Year career to match an England 10 Year one. He played a fair bit longer than Steyn, and a lot longer than Ambrose. He also has a fair few more wickets than Ambrose, and nearly as many as Steyn. Would you rank a bat scoring less runs in more games ahead of one scoring more in less?Played less Tests than Steyn and Ambrose, let alone McGrath.
It's a fine margin, 10-15 Tests, but I'm going to credit the fast bowlers who did play them and maintain their stellar record, over the ones which we would surmise could. After all, when we talk about the top 5, we are only dealing in fine margins, as they are all obviously exemplary.