Distinction between Selector and QualifiedIdent?

[nicuveo]

The grammar establishes a distinction between those two:

QualifiedIdent = PackageName "." identifier .
PackageName    = identifier .

PrimaryExpr = Operand | PrimaryExpr Selector // ...
Selector    = "." (identifier | simple_string_lit) .

And the specification clearly states that selectors do not apply to packages:

For a primary expression x that is not a package name, the selector expression [...]

My question is... why this distinction? The playground treats a package expression as a struct, in which fields correspond to the exported values of the package. For instance:

import m "math/bits"

result: m

evaluates to

import "math/bits"

result: {
	Lsh:       bits.Lsh
	Rsh:       bits.Rsh
	At:        bits.At
	Set:       bits.Set
	And:       bits.And
	Or:        bits.Or
	Xor:       bits.Xor
	Clear:     bits.Clear
	OnesCount: bits.OnesCount
	Len:       bits.Len
}

There is no reason not to think of m.Set as a Selector in the m struct corresponding to the values of math/bits. Furthermore, doing so solves an ambiguity in the grammar: it's not currently possible at parsing time to decide whether a.b matches the Selector or the QualifiedIdent rule, since both have the exact same syntax. If QualifiedIdent is discarded, then it solves that problem.

I'm curious as to why that distinction exists?