A Spectrum Analyser with Tracking Generator (SA/TG) and a Vector Network Analyser (VNA) are not the same thing.
They can be.....Siglent SVA series.
First I bought a SSA3032X then replaced it with a SVA1032X which has proved to be much more useful.
SSA3021X Plus can be improved to become a SVA1032X !
Yes, yes, there is always the exception.
Typically these instruments are VNAs with SA functionality added. But as modern front ends are digital ther is little physical difference on many of them. The VNA does of course have to have at leas one directional coupler or Return Loss Bridge to be of any real use.
I specified a R&S ZVL VNA with option K-1, which adds spectrum analysis, at work. Gets used mostly as an SA but having the VNA means we don't have to pay to get amplifiers, cables etc calibrated, just check them at time of use with the VNA function.