@koolbreeze > I think it's a misunderstanding of how sync functions... taking your scenario from above, I've added my comments in bold as to how it actually works.
Track on deck 1 playing at 100 bpm. No sync engaged. Load track to deck 2 and press syn on deck 2. Deck 2 track will sync to deck 1 track. 100 bpm. Deck 1 is now set as MASTER. If i move pitch slider on the MASTER deck, the tempo should change accordingly on both decks.
I now mix over to deck 2. When i load a new track to deck 1 sync remains enabled and the track on deck 2 will become the MASTER and remain at 100 bpm regardless of where my pitch fader is - this is known as a "soft-pickup" because the virtual position of the fader doesn't match the location of the physical fader. If you want to change it, move the hardware fader to the current pitch position and make an adjustment. If i now hit sync on deck 1 (if it wasn't already engaged). The bpm should sync with deck 2 bpm whis is 100bpm, which it will.
You can move the pitch fader on the master deck to achieve this goal; the pitch fader will only "open to infinite" when your pitch range is set to WIDE range.