This is a "loaded" but fair question because we're talking about DC on a miter saw to start with and this one is also a Kapex.
The short answer is that it's actually slightly improved because that block helps force the saw dust through the kerf in the block. Almost like a funnel if you will.
The longer answer is all around DC in general when it comes to miter saws. In my opinion, regardless of brand, they are all horrible at DC, even the Kapex! I see so many posts about how great the Kapex is and I completely disagree with that statement. It might do a little better than the others but, it's still not good! Even with a dedicated CT, the area behind my saw is still full of saw dust each day. There is also a fairly wide dust field both to the left and right of my saw each day.
At some point, I will add a drop on my big DC to this area to (hopefully) improve the DC on this tool. In reality, I think everyone is going about DC on this tool all wrong! All the gizmos and gadgets people come up with for DC on the miter saw is geared around collecting dust at the source. I think "we" as a community have proven this to be an impossible task! Just my opinion but, I think we need to try and contain it in a larger general area and then collect the dust from underneath. Instead of collect at the source, we need to control, contain, and then collect because we've pretty much proven the last step doesn't work well without the first 2 steps.
I'm thinking about a project in the future to insert my HCM into the top on my miter station. If/when I do this project, I may add a drop from my DC into this area (since the top will be off the bench) and hard pipe under the back of my miter saw to cut down on the amount of clean up I need to do each day. Pretty much treating this entire area like a down draft table.
Sorry for being long winded but, this is always a hot topic of conversation.