In altera Transceiver, why some protocols need rate match fifo, some don't need?

You can use SRIO to transmit among different boards... as long as the boards have a common clock reference.

It needs to be the same source, crystal, but you can distribute the clock among multiple boards using cables, backplanes, whatever.

Ie, SRIO is used in ATCA/µTCA crates, but there's a reference clock distributed by the crate to the boards.

But if you have different oscillators, then it's a no-go. You need another protocol which is elastic.