In simple QAM modulation symbol synchronization is crucial: the samples need to be taken (or interpolated and resampled to ) exactly corresponding to the time when the symbol was emitted.
This is why symbol syncronization methods like Muller-Muller was developed. I call this - for the sake of contrasting it with coarse OFDM symbol syncronization (achievable without interpolation and resampling) - fine-symbol-syncronization or smaller-than-time-interval-between-samples syncronizaiton.
Now, the question is, if such fine syncronization is important or not for OFDM. In OFDM there is the cyclic prefix which is much longer than the time interval between samples and there is also the FFT. It is not clear if in the case of OFDM the fine-symbol-syncronization is really neccessary. It might be that the guard interval+FFT makes it unneccessary.
One reason why fine-syncronization should not matter is that the purpose of the guard interval (cyclic prefix) is to make demodulation insensitive to channel response (multi path due to reflections).
Is it important with OFDM to carry out fine, i.e. smaller-than-time-interval-between-samples syncronization ?
EDIT: this book seems to discuss this question in Section "5.2.4 Synchronization Errors", it says that timing offset causes rotation - increasing in strength for sub-carriers further away from the center - need to read it more carefully.