What do you mean you rack the beer into the bottling bucket with the tubing curled? I place my tubing about an inch from the bottom of the bottling bucket and then keep it there the whole time, until my beer is done siphoning. Is this ok or should I be moving the bottom of the tubing so that it is always above the beer and not submerged? Hope this makes sense.
What I always do is:
1) Boil 2-3 cups of water, add amount of sugar pursuant to one of the many priming apps found on the web. Boil for another 30 seconds, remove from heat, cover with the lid off center so it cools in a reasonable timeframe. Stick in fridge to cheat once it's below 150 or so. Pull from fridge when near room temp.
2) Spray StarSan like mad all over the outside of the tube, my hands, the inside of the tube, and whatever else is near me. Dog doesn't appreciate it all that much, but his breath is great now.
3) Attach the top of the tube to the auto-siphon/cane, and lay the bottom 12 inches in the bottom of the (StarSanitized) bucket. Every hose I've ever gotten seems to have a permanent arc due to being on the spool originally. This arc helps curve the hose along the flat surface in the bottom of the bucket.
4) Pour priming sugar solution in the bottom of the bucket.
5) Start siphon, and watch it kind of swirl gently along the bottom. The swirling seems to degrade as the bucket fills.
6) Once siphoning is done, I gently pull the hose, and rinse it. I then GENTLY stir the beer, just to make sure everything is mixed well.
7) Lift bottling bucket onto counter top, after moving the carboy out of the way.
8) StarSan the hose again, install on bucket spigot and bottling wand, and away we go.
Long way of answering the question, but there it is. I personally don't like leaving an air gap between the end of the hose and the top of the siphoned liquid, but I don't freak out if I accidentally splash it a bit. I've learned that if reasonable measures are taken, oxidation is something that can be mitigated. I've made HORRIBLE mistakes with agitating/splashing beer pre-bottling, and every one of them tasted fine.
Different people will take different approaches, your mileage may vary, see local dealer for details...