I asked the examiner who did my IMCr in February to sign the language form. He wasn't very sure about it but signed the form anyway.
Two days later, I did an "in person" application at Gatwick. When I collected the licence some hours later, I asked the lady if the language had been amended. She assured me it had and that I was now level 6.
There's no difference between the old language (level 4) entry and my reissued one.