No, because in gun barrels there isn't (theoretically) any micro pores created by a weld. If it was a simple thing like cleaning we wouldn't express the concern beyond suggesting anti corrosive compound cleaning methods.
This isn't anything is going to cause your cannon to fail today, your cannon may never fail. It's circumstance that raises the possiblility that it will fail in the future.
Writing this makes me think of a couple cannon accidents that have been reported here on the board. A common thread reported in the two accidents Thurston Co. Washington was they shot the guns for years with out a problem. Now granted there may be other contributing factors in those accidents, I have to wonder if this concern of corrosion in the micro porosity may have played a part.
I am really sorry to have to be the spoiler and tell you this after you have spent your money. If you had come to us first we would have warned you. Hopefully others will read this and be fore warned.
It has nothing to do with GreyStar cannons. They build a beautiful gun. If were I were closer to them than I am Hern, and I was in market for this type of cannon, I would buy from them, but I would specify a seamless liner.
The sad part is that if one of these seamed liners fails it probably will be long after the company the made the cannon ceases to exist.
Shoot, your cannon. Do the periodic inspections. And at the first sign of concern fill it full of cement.