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Short answer, no, not unless you are using a Film camera with film TTL flash.
The SB-800 SU-4 mode can be Auto or Manual. Auto in flash has two meanings. In this SU-4 case, it means that it starts its flash with the triggering flash, and it stops its flash with the triggering flash (if you can carefully aim the sensor at the triggering flash). So, the way film TTL cameras control their TTL flash is to start it at full power, and quench it when the exposure is deemed sufficient. If the Auto SU-4 flash is following this (stops at the same time), it can simulate multiple TTL flash, and also stops when exposure is sufficient (meaning film TTL mode). However these flashes are NOT metered individually at all, whereas the idea of digital Commander TTL is that it does meter two flash groups individually.
With modern digital iTTL, there are preflashes first (to be metered), and SU-4 will simply trigger at those preflashes, before the shutter is open. Which likely messes up the metering of that preflash. The SB-800 is fast, and if not at full power, it may have ability to trigger again at the final flash, maybe. However, this final flash was preprogrammed with a power level, it is not quenched. You cannot call this TTL in any sense. You cannot call it anything but a dumb plan. SU-4 is for manual flash mode.