Model Tags for Model Names with 1.5 and SDXL Variants

How should one tag a model if a SDXL Model is named after a SD 1.5 Model? For example, sweetmix now has a variant based on SDXL, but it was originally line of 1.5 models. Both the XL and the 1.5 models are maintained on the same Civitai card, just as different versions. If an image is uploaded using SDXL version, should a new tag called "sweetmix-xl" be created, or should the original tag be used since it is found on the same model card?

Here: Sweetmix XL/Pony. Generally we want to split SDXL from SD1.5 because while SD1.5 versions might be slight iterations on the preceding model, SDXL are essentially a new one because they're based on a completely different architecture.