How to connect two LED strips (APA102/SK9822) to Arduino UNO?
I don't know about SK9822 LED strips, however the other type of led strips can be used with every pin; this is to support multiple LED strips.

Because every LED strip has its own CLK input (wire), it would be inconvenient to share them... I'm not sure if it is possible practically, because the timing is critical and if you have just one 'master' CLK signal than the data signals for all LED strips should be sent in time. Also writing the library would be more difficult, since there is a relation between a (shared) CLK signal and other data lines.