I think one of the purposes of [cpp.import] p.2 is to say that the import directive is entirely replaced by the same tokens, except for the mentioned changes (e.g. import token replaced by the import-keyword token). Is this the intention?

Or is it that because the import token is replaced by the import-keyword token, the line is not considered a preprocessing directive anymore, therefore it does not get removed?

Editorial teleconference: This area is in flux and likely to change next time.

There are now clarifying notes in cpp.module:

The module and export (if it exists) preprocessing tokens are replaced by the module-keyword and export-
keyword preprocessing tokens respectively.
[Note 2 : This makes the line no longer a directive so it is not removed at the end of phase 4. — end note]

and in cpp.import:

In all three forms of pp-import, the import and export (if it exists) preprocessing tokens are replaced by the
import-keyword and export-keyword preprocessing tokens respectively.
[Note 1 : This makes the line no longer a directive so it is not removed at the end of phase 4. — end note]