PreRelease comparison bug?

[vsimon]

In looking at the ComparePreReleases test cases...

func TestComparePreReleases(t *testing.T) {
	cases := []struct {
		v1       string
		v2       string
		expected int
	}{
...
            {"5.4-alpha", "5.4-alpha.beta", 1},
}

I'm noticing that 5.4-alpha is larger (has a higher precedence) than 5.4-alpha.beta. However when reading over the precedence rules of pre-releases in semver (https://semver.org/#spec-item-11)

A larger set of pre-release fields has a higher precedence than a smaller set, 
if all of the preceding identifiers are equal. 
Example: 1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-alpha.beta < 1.0.0-beta < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0.

In this test case, all the preceding identifiers are equal - "5.4" - and the larger set "alpha.beta" has a lower precedence than the smaller set "alpha". Shouldn't it have a higher precedence?

[vsimon]

I'd be willing to create a PR maybe if this is a problem.