With the continuous improvement of out-of-order execution, the SMT gains have been diminishing from Zen 1 to Zen 4. However you are right that Zen 5, like also

With the continuous improvement of out-of-order execution, the SMT gains have been diminishing from Zen 1 to Zen 4. However you are right that Zen 5, like also the Intel Lion Cove core, has a jump in the number of available execution resources and it is likely that out-of-order execution will not be enough to keep them busy. This may lead to a higher SMT gain on Zen 5, perhaps on average around 30% (from typically under 20% with Zen 3 or Zen 4), like in the Intel presentation where they compared a Lion Cove without SMT with a Lion Cove with SMT. In the context of a hybrid CPU, where the MT-performance can be better provided by efficient cores than by SMT, Intel has chosen to omit SMT, for better PPA (performance per power and area), but in the context of their future server CPU with big cores, they will use cores with SMT (and with wider SIMD execution units, to increase the energy efficiency).