Sylas is still an AP Bruiser, as he was intended to be since the start. They already fixed his passive scalings (the AD is just 100% as normal, AP scaling unchanged, base damage scales harder with level). The only real important change is that he's less bursty and now he's bulkier, with his E shield being stronger but only being on E2.
More importantly, there was a time on the PBE when his passive had a 120% AD scaling, but the AP scaling was never removed like how Professor Akali says is the case at the start of the video. At the time the video was uploaded, the changes in it were already outdated, and from what I recall, the changes he said in the video, save for increased W healing and E2 giving shield instead of E1, weren't actually the case. A quick skim over Surrender @ 20 verifies this.
It's not a rework, either. It's an adjustment. The only changes here are numerical changes, save for the change on his E.