First,let me say I intend no disrespect in my response.You have already told us you are in unfamiliar territory.
There are some "Well,gee,it could be he means....." paths I could go down,
But as it is,your question does not add up to anything real world that I know of.
There is either a communication gap between you and the seller,or the blind lead the blind.
There is such a thing as reboring-re-rifling for shot out or damaged bores.If that is done,a 30-06 does not remain a 30-06.It becomes a 338-06 or a 35 Whelen.The bore must get larger.
I doubt anyone is cutting a new rifling groove down the middle of the existing lands.
Ask the seller to re-explain it in front of a gunsmith.
And,likely,no,I would not buy it.Unless you really know what you are seeing,I'd stay away from anything "special" that someone wants to get rid of.
Now,if he meant rebarrelled,that is a whole new ball game than rebored.