The article actually covers that. With the existing L1 signal the multipath signals overlap each other and its hard to find out which the original signal was.

The article actually covers that. With the existing L1 signal the multipath signals overlap each other and its hard to find out which the original signal was. The newer L5 signal is much shorter, so multipath signals will show up as individual peaks, and the receiver can simply pick the first signal, cause that will be the direct one.