Nice denu... "using" the same sort of semantical argument I might propose... but as this conversation is trying to differentiate between a submissive and a bottom, it is all about context.
I think that context lies in the concept of a continuum, as thir and I have separately pointed out in other related and non-related threads. The "boundary" if you will, between the definition of bottom, sub, and slave, is different for each of us. So you can play with the word and use it at the far end of the continuum but you can't use it as an argument against my statement and in the same breath agree it isn't the same.
I'd argue that few people would equate my willingness to relinquish control in one arena as being the same as submission. It's just control of the airplane (or other venue) that I relinquish. In fact, having done so, if the pilot said he now intended to break covenant with the terms of the "contract" negotiated for this event, the flight, I would have every right to end his control, whether by leaving or wresting away his control. Far more like bottoming in a scene than submitting to a dominant.