Why is method so important for a thesis?
Computer science, huh?

I think that the issue many forget with the name "computer science" (and that's why "informatics" as a word exists at all) is that it's not about computers. Well, that was harsh. It's not totally about those small silicon dies and such. It's about information processing. And it's about ideas.

Basically, "we wrote a program, hurdur" does not cut it. Even "we wrote a program, here is the github" does not cut it. "We got this cool result" is cool. But what most people would be interested in – on a large scale, in 10-20-100 years, – is not that you used an i7 chip. It's not that you wrote it in Python. It's the idea. The essence. The thing you write in methodology. Your very future readers would not care about your source code (even if it's available). They would be trying to implement your method in SuperCoolFunctionalNeuronQuantumSnake++#XXL that would be popular in 40 years. And what they'd read, is methodology.

tl;dr: Methods would persist, programming languages and even results would not.