It's understandable to be irked, but simply put it's the core abilities mixed with overall aesthetic that points me in the direction of CON/WHM and THM/BLM. Conjurer has always been portrayed as nurturing, and Thaumaturge has always had a rather foreboding atmosphere, centered around death and all.
Conjurer has Cure. Cure has been white magic in every single FF title. Ever. Having a White Mage that doesn't have cure makes no sense. However, THM has banish and dia, which are spells akin to a WHM.
On the other hand Conjurer has elemental spells, which are iconic of a Black Mage. However, THM also has dark magic, which is also a Black Mage trait.
IMO, I wouldn't be surprised if they did an overhaul (as they said they're tweaking class abilities) and swapped a lot of abilities between the two classes. I also wouldn't be surprised if the jobs themselves just gave access to said abilities the classes lack. There's ways to play it off lore-wise.
I'm sure SE has something worked out that will surprise us yet. They're just not going to have White Mage using "Sacrifices" instead "Cures", and they're not going to have Black Mage without elemental magic.