So the sockets aren't GFCI protected. If you are ever working on a mains PSU circuit, or other mains control circuit you should therefore use a plug-in GFCI feed the device you are testing (D.U.T.). If you are testing or using SMPSUs that may be of dubious far east origins, I would also recommend a GFCI, even if you never open their cases. Get one and use it - its far cheaper than a funeral!
From the point of view of ESD grounding, the test iindicates you can use both sockets. The built-in safety resistor that is supposed to be present in all ESD grounding accessories will prevent any hazard or other issues if there is ever a small potential difference between their grounds.
However, I wouldn't trust them if you need two devices to have the same low impedance mains ground as you don't know how big the ground loop is - it could go right back to the panel, or in a large apartment building, right back to the utility company's transformer! Therefore, if you need your D.U.T. to have a common ground with your test equipment, feed everything from a good quality socket strip plugged into *ONE* of the outlets to minimise the ground loop size. This typically apples for scopes, signal generators, PSUs with grounded output and PC based USB connected test equipment, as any significant ground differential can cause $expen$ive$ damage. If you are setting up a permanent workbench with mounted socket strips fed from separate wall outlets, bond all their grounds together at the bench with heavy wire or braid when you fit them to mitigate this issue.
One nasty 'gotya' is mains powered soldering irons and many soldering stations typically have the tip directly grounded without a safety resistor as the leakage current through the element insulation when hot may be too high to permit including one. If you use the soldering iron on the D.U.T. without disconnecting other grounds to it, and they are plugged into different wall sockets, if there is a large ground loop, induced transients may be enough to blow sensitive semiconductors on your board!