Once you see the resemblance between the names Sifo-Dyas and Sidious, you just can’t unsee them. It was definitely intentional. They were clearly meant to be one and the same at some stage in development.
They were. George made a typo of Sidious as Sido-Dyas. It was originally the name of a “Jedi” they had never heard of. In reality it was an alias. The story evolved and he changed it to a character named Sifo-Dyas and planned to explore his backstory in Revenge of the Sith. He changed his mind. It’s curious because he remarks in the commentary of Attack of the Clones that the Clone Wars is very important to the whole epic of Star Wars. It makes me think he may have saw potential for it as a way to tie into his Sequels if he were to ever make them. Same with Anakin’s origins not getting their original explanation at the hands of Palpatine. The story grew and evolved as he added new pieces to the puzzle.