We create the transactions table on step-up via a DBDirectClient call. That will inherit the default writeConcern, which is a problem if the user changed it from w:1. In that case, the call will wait on that WC immediately, while also holding locks (particularly the RSTL in mode X, from the step-up hook). We do not want to do this, as that can block other processes, including servicing find commands for replication.
We should instead create the transactions table via the storage interface, as that will give us w:1 in all cases.