I want to point out that Sha Lek Highway is designated as an expressway, while Airport Road is not.

If the standards require that only numbered expressways get "=motorroad", then I do not understand why this section of Airport Road should also get "=motorroad". I see no problem demoting the highway down to "=primary" the instant it is no longer a numbered highway.

For example, Route 7 (TKO side) instantly demotes to "=secondary" right as it ends.