This is reasonable. After all we've been developing software for a few decades now. Surely we should be able to learn from the experience of others. The Variability of Methodologies To be brutal about it most methodologies are statements that a methodologist makes based on what he did once. I suspect most of them are based on what they wished they'd been able to do.
Software is also incredibly variable.
For a start one of the key variables in software is people. Different methods will work differently with different people. Company cultures also have a big effect. There's also the style of the software. I don't belive a process designed for telephony is appropriate for information systems, is appropriate for games.