DBMS_SPACE_ADMIN and migrating DMT -> LMT

Guys,

I'm handling with the matter of migrating large DMT tablespaces (8000+, some with millions of rows) to LMT. I first thought of exp/imp or alter table move to a brand new LMT. However, I found on the documentation a procedure DBMS_SPACE.MIGRATE_TABLESPACE_TO_LOCAL.

I was wondering how could that procedure relocate existing extents that violate new LMT policies and, according to note 120061.1, it doesn't. If I understood well, DMT migrated with DBMS_SPACE_ADMIN still allow users to specify their own storage parameters and, so, fragmentation can still be an issue. Is that right?

Further, it seems that DBMS_SPACE_ADMIN just creates bitmaps on a DMT, so can I conclude that the operation is fast and with little impact? DBMS_SPACE_ADMIN seems to be a faster and less risky way, but will I get the benefits of a LMT with that method?

Any insights?