Correct! An FI without CPL knowledge may only provide flight instruction for the LAPL(A), any ratings which can be included on the LAPL (e.g. night or aerobatic raitngs) and addition of privileges for other classes which may be flown using a LAPL (e.g. adding TMG privileges). Of course the FI must also be qualified to provide such instruction.
However, if the LAPL-only FI also holds a CRI certificate, he/she may provide any necessary class rating instruction for qualified pilots - such as variant differences training and refresher flight training.