Not sure 96 minutes will be sufficient in all load-following cases (bar a huge and therefore very expensive fleet of reactors). A gas turbine is way ahead here. Moreover in existing reactors the frequency of such adjustments is limited, for example "no more than twice a day, with a minimal 5-hours pause between modulations, and no more than 150 modulations per year". Approaching limits adds maintenance time (at shutdown state). I don't know if SMRs alleviate this, but given the causes I doubt so.
We will likely have sufficient battery storage where 1.5h would be acceptable though not quite ideal. It still requires quite a bit of storage, but its entirely doable for seasonal variations (the harder problem) and perhaps even daily cycles (the lesser problem).