This is not true. Our Head of training (who is an IRE and an FE CPL) usually signs this section for all of our students. The instruction for this section states 'To be completed by the holder of an Examiner Certificate issued in accordance with Part-FCL', not the examiner who carried out the test.
The section does not say that the examiner signing it carried out the test, only that 'the test has been completed' and the applicant 'meets the experience requirement for licence issue'. Therefore it can be signed by any examiner.
I thought so too until the Civil sent back an application, so just jump through that hoop directly. I haven't found a problem though as emailing a copy always works.
Unfortunately the goal posts seem to change depending on who processes the application at the CAA.