This change is FANTASTIC. The old tech group malus was TOTALLY ridiculous from both a historical and gameplay perspective. African nations were far more sophisticated than they're given credit for. Great kingdoms like Mali and Kongo and the trade forces like Mombasa were on par with most of the world from a military perspective until the Europeans, having much greater naval power, became capable of sending gunboats down the lenght of Africa. Even then the Europeans had no way to colonize or invade past the shores due to attrition, pre-industrial supply lines and, frankly, because those Africans who lived in kingdoms or other larger societal structures were perfectly able to put up a fight. The only reason Africa didn't show up regularly in European conception of "world powers" is because the continent is separated from Europe by one of the most impassable geographic features in the world, the Sahara Desert. To the Europeans of this era, the enormous and quite sophisticated African nations were mostly relevant as trade partners - due to enormous amounts of gold and slaves available. It's obviously a terrible thing to think about, but it's important to remember that the Europeans didn't really take many slaves in Africa. Rather, it was large and powerful African nations that traded the slaves for gold, guns, other weapons and luxury items. Which goes a long way towards defeating the stereotype that Africa was "just a bunch of disorganized savages the Europeans could invade at will", which is unfortunately exactly what the current build of EU4 is portraying.
Putting the Sub-Saharans on par with Indians or the Chinese also makes sense from the perspective that the Europeans started conquering lands from both Africa and the Malayans and Indians at virtually the same time due to relatively recent progress in naval technology and improved guns, which allowed massive European ships - practically floating fortresses - to show up anywhere in the world, en masse. Some areas were still harder to conquer than others due to various reasons, of course. Most importantly, some areas were far more profitable than others, partly due to attrition and trouble with the locals. This all went on rather later in the game - in fact, the new tech level malus will probably allow the African nations to keep up with the Europeans to enough of an extent that they will start falling behind around the time they did historically. It will also allow for a MUCH more interesting gameplay from the perspective of both European and African starts.
I'm really excited to see EU4 make this important change I've been pining for for a while.
Edit: By the way, the reason Europe developed naval technology so early and at the rate that they did is plainly obvious if you look at a world map. Europe easiest has the largest coastline-to-size ratio of any other continent due to massive inland seas which allowed people to travel enormous distances extremely easily. This allowed for trade routes that led directly to the development of Egyptian and Greek civilizations, allowed the Roman Empire to even exist (due to its massive capacity for grain imports), allowed the entire Viking era to be a thing, all of which led up to the Europe we know from Europa Universalis - Venice, Ottoman Greece, Spain, England and France all being massive naval powers. European history is almost defined entirely by naval history (plus mass migrations from Asia, but that's a CK2:Charlemagne thread.).