Sorry, I missed your post when I made my last reply. I am not a body armor/ballistics expert, but I have done a lot of research and have some experience in the subject. I will share some of what I have learned in my research.
Several of the plates you are referring to are certified under the NIJ 101.04 (2005 Interim) requirements such as the Velocity System PSA4. These plates won't show up in the current NIJ certification list. However, they retain their original certification. Many companies offer plates under the old spec and the new spec. These plates are often very similar, if not identical. For example, the Highcom 4SAS7 and the 4S17 are essentially identical plates, but the 4S17 has refinements, namely extra padding for the drop test, to meet the .06 spec. Since many vendors are actually selling rebranded plates (LTC, Tencate, Hesco, etc), the model # in the NIJ .06 certification list may not exactly match the company's own "model #." Most companies keep the original plate mfgs model # for the NIJ purposes. Additionally, some companies may sell the exact same plate from the same OEM mfg, but one company may decide to get it certified and the other may not.
Then you add in the realm of "special rifle threat" validated and independently tested plates. Since the .06 standard addresses SRT plates, many companies make them. Most of these plates are designed around specific applications or threat profiles such as the Velocity PBZ (SA and ICW versions). So these companies don't bother to take on the extra expense of getting them NIJ certified. They just conduct independent testing. Some companies offer plates that are independently tested to the full NIJ standard, but not certified. Again, usually, this is to save cost. However, be wary of some unscrupulous vendors selling plates that may not be high enough quality to pass the test. Look at the independent test results. The test info should include whether the test was conducted to the full standard or the abbreviated standard.
If you are looking at level III/IV plates, again, be sure to look at the actual test results. A level III/IV plate should have been tested to meet both standards (multi-shot 7.62x51 and likely a single shot 7.62x63 M2AP). Usually, they are ICW plates. I don't know of any NIJ .06 certified III/IV plates. These will usually be independently tested.
Lastly, some plates are tested to the ESAPI standard (military standard). This is similar to the NIJ level IV, but is considered more stringent. These would be considered special threat rated/independently tested plates. These plates may or may not even be tested to the NIJ standard. The Velocity System PB Lvl IV (ESAPI) plates meet the NIJ .04/05 as a stand alone plate and the ESAPI standard when ICW their level IIIA backers.
I hope this helps. I welcome input from any of the SMEs.