This issue was reported during reviewing JDK-8329603 [1]. There has been the feeling that that method does not belong to G1BlockOffsetTable as it covers a very specific situation in G1.
[1] https://github.com/openjdk/jdk/pull/18634#discussion_r1553170536
[1] https://github.com/openjdk/jdk/pull/18634#discussion_r1553170536