It's because SKIPIF needs the following syntax

{ SKIPIF expression1 comparison-operator expression2 }

so e.g.

{ SKIPIF "1" = "2" }

or

{ SKIPIF { COMPARE "1" = "2" }  = 1 }

should yield all the records,

{ SKIPIF "1" = "1" }

or

{ SKIPIF { COMPARE "1" = "1" }  = 1 }

should yield no records.

As far as I know you cannot replace

expression1 comparison-operator expression2

by a scalar value of any type and have SKIPIF do anything except SKIP
everything, e.g.

{ SKIPIF 1 }

{ SKIPIF 0 }

{ SKIPIF -1 }

{ SKIPIF "A" }

will all yield no records, and by doing

{SKIPIF { COMPARE "1" = "2" } }

you are in effect doing

{ SKIPIF 0 }

Because "1" and "2" are strings and will NEVER match. Since they never
match, all records are skipped.

grep