It absolutely was contradictory, it said of 5e books only the core was canon (to 5e), then he starts listing stuff from other 5e books as canon, plus it contradicts what Crawford said. Like I said the post can safely be ignored, BUT with the following exceptions.
1: having multiple seperate canons for different editions, the novel line, comics, ect..., instead of decanonizing stuff like we thought they were originally going to do, is setting the up the next FR book for a splitting of the Forgotten Realms & D&D multiverses into a system of parrell worlds/multiverses, and the book won't just explore the present, but open the door to alternate timelines/multiverses, like a timeline that didn't advance past the Grey Box, because the ToT never happened, and a FR multiverse were the Plaguelands still exist because the Sundering never happened for example. This marvel style metaverse for a lack of a better name, will be the theme for this FR book the way Horror was for Ravenloft, Magitech/Pulp was for Eberron, Guilds were for Ravnica, and MtGied Greek Mythology was for Theros.
2: Future stories won't worry about previous canon, because they are in different timelines, no don't be surprised by inconsistancies.
But the way this was explained was a hot mess, and could have been done better.