When trying to use the test for block command inside a command block it will pass as true if the blocks there, however if you add any argument like facing direction and or on/off it will still only pass true if the block is there or false if its not. Intended behavior is pass true if the block is there and meets the arguments false if its not there or does not meet the requirements (like a lever being in the on/off position or a button being pushed in)
This issue is being tracked at MCPE-194284. It will be fixed in 1.21.90.