I'd like to clear something up, not all the bolts sit in holders that are taped down, some are moulded.
Therefore saying you may as well use 3M as the the bolts are taped down isn't accurate.
I think it's likely the spoiler will stay on fine with just tape, but I bolted it because Toyota recommended it and as I have bolts I can tighten the spoiler down more at any point in the future if it becomes loose.
And mine did start creaking, quick tighten all good.
You can't do that with tape.
Make your own choice but with all the info!