I recently brewed a pale / ESB with water that I lowered the cl/so4 ratio to 0.2 (for the entire wort volume). The grain bill was similar and Yes, it still does have a great malt flavor. I used Wyeast 1968 which I think plays a role. However, my IBUs were much lower. I am not sure I could taste much malt flavor with 100 IBUs, but everyone tastes things differently and I am not a BJCP judge.
As I understand it, the so4 doesn't technically change the bitterness or IBUs in a beer, but rather changes the taste perceptions of it. I think it provides a sharper, crisper, or cleaner bitterness flavor rather than a harsh or muddled bitterness.