Parts of test structures sometimes remain after running /test clearall

Using /test clearall to clear all test structures can leave blocks behind if there are multiple test structures close to each other.

How to reproduce:

The attached data pack (MC-279598.zip) contains an example test instance that is 3 blocks wide on the x axis.

1. Create a world with the attached data pack.
2. While facing south, execute the following command:

   /test run mc-279598:test

3. Move 4 blocks to your left.
4. Execute the command from step 2 again.
5. Execute the following command:

   /test clearall

   → 3 bedrock blocks and 1 accept block remain.

Expected result:

/test clearall would clear all blocks placed as part of test structures.

Observed result:

/test clearall sometimes leaves some blocks that are part of test structures behind.