In the updates tab for ESXI hosts in a vSAN cluster, version 7.0 U3p its not listed in the baseline groups to patch the hosts to.
The updates tab is located by selecting the ESXI Host > Updates > Baselines > Baseline Groups > Baselines
vCenter 7.0.3
ESXI 7.0.3
vSAN Stretched Cluster
This is not possible using the automatic baseline recommendation.
ESXI 7.0 U3p is an express patch which means by design it is not included in the Lifecycle Manager catalog when using vSAN.
The catalog is a file where where release recommendations are maintained for Lifecycle Manager.
Lifecycle Manager does not recommend express patch or host patches, it will only recommend ISO or upgrade baselines and general patch baselines.
The next automatic patch release which can be used in this scenario would be the ESXi70U3q-23794027.