Aside from the Pro Controllers with weird bugs, I can say that the Dpad having incorrect inputs is by design, I just tested my Wii U Pro Controller Dpad and it's no different to the Switch Pro Controller Dpad.
I went to test Super Street Fighter 2 on Wii U and was pressing left and right without lifting my thumb and an incorrect input would happen due to the way the Dpad is designed.
Now, you may be shocked to hear this but there is one Nintendo Dpad I have not had this problem with because I've been playing a game on it over the last week.
The original Nintendo DS Dpad does not have this problem at all and I couldn't do an incorrect input whatsoever, the way that Dpad is designed is that the Dpad feels very tight. If I put my thumb on the points of each direction, I can move it in that direction but it's too hard to move it elsewhere​.
If I press down on the DS Dpad but then move my thumb left and right on the down direction of the Dpad it will be difficult to do so because the Dpad has little movement to the sides of its edges.
And as I said before, the best freedom of movement is in the centre of the Dpad, I could put my thumb on the centre and press left and right with quick presses without lifting my thumb and it will not produce an incorrect input.
However, since both the Wii U and Switch Pro Controllers have a Dpad that is more loose. I can press left or right while pressing down and moving it side to side.
So in summary, Nintendo DS Dpad is tight: doesn't cause you to make mistakes.
Wii U and Switch Pro Controllers Dpads are loose: Can cause you to make mistakes if you don't lift your thumb when pressing the opposite direction.
So, it seems maybe the split Dpad should have been put on the Switch Pro Controller as well because it feels tight and I know I can type fast with it when logging into the eShop but I make mistakes with the Pro Controller.
Hence, a bigger split Dpad on the Pro Controller would have been better and not have caused this issue although this issue is by design and has been around since the Wii U Pro Controller but, it looks like this issue only came up now and not with the Wii U Pro Controller because I bet people are being too sensitive to things with the Switch due to every problem that keeps getting announced. lol