It is not yet known whether such concerns are true. But if the Hong Kong version of the National Security Law is a "national law", it is not impossible for it to be handled by a "national agency". In this situation, similar to the United States, there are federal police (for example, it is the responsibility of the federal police to deal with illegal immigrants), and there are also state police.
National security may be analogous ghost mannequin effect to the federal police, which is specially responsible for the enforcement of the Hong Kong version of the national security law. Direct legislation by the Standing Committee of the National People's Congress is likely to be completely inconsistent with the requirements of Hong Kong common law, and it is difficult to implement it in Hong Kong, so it is most convenient to move it back to the mainland for implementation. If this is the case, of course, it will be very detrimental to Hong Kong.
Compared with the Fugitive Offenders Ordinance, Hong Kong has withdrawn the amendments to the Fugitive Offenders Ordinance. But in this way, even if the Fugitive Offenders Ordinance is not revised, it can still be "sent". The actual situation is much worse. Under the Fugitive Offenders Ordinance, the "delivery" will also go through two procedures, including the Chief Executive's gazette and the court hearing. Although some people criticize it as a fake, it may not even be "fake" now.