It's not clear if the original poster got this issue cleared up or not.
Drawing on past experience, with a diesel engine of any variety and any model year that supports passenger car OBD or OBD II diagnostics, it is vitally important to test any "code reader" before making a purchase. Some of the larger brick-and-mortar auto parts stores (e.g., O'Reilly Auto Parts and AutoZone) will scan your vehicle if the Check Engine lamp is on, and this is a great test of the tools they sell. There's also at least one online-only store that has a Bluetooth reader for use with PC or smartphone has a generous return policy.
The tool manufacturers have to do all the development work for their tools - they don't get any help from the vehicle manufacturers on older vehicles, and with Right to Repair they have the ability to license access to workshop manuals for newer vehicles. Either way, though, they must still write software to read the codes (from up to 5 different network types) and interpret the codes (at least 3 different data formats). Companies developing the low-end readers - and no other product - may not have the budget to support all vehicles. (Probably more than anyone really wanted to know...I lived this stuff for about 10 years.)
Also drawing on past experience, some of the higher-end handheld tools that say "WiFi required" or "cellular required" only require that connectivity for accessing a "knowledge base" that has additional information. Professional-grade tools usually need the connectivity for software updates - whether for the tool (common) or for the vehicle being repaired (less common).
