In short, unless the pro shop strung the frame ATW, they probably did it incorrectly (bottom to top). Head mandates that their frames be strung top to bottom, and as far as i know, don't OFFICIALLY support ATW patterns. Thus, as an amateur stringer, I suggest doing your frames two piece. Mains top to bottom.
As far as "does it matter:" This is where the opinions are going to differ a lot. Pro shops get away with poor quality work because they can afford to. They will RMA directly to the manufacturers, and most times will receive a frame back in return because they are resellers.
I think you SHOULD do a two piece top to bottom as an end user, but it's not going to shatter your frame otherwise. It's smarter, and better, and more "correct" to string top to bottom, FYI.
As far as racquets with a "one piece pattern," it is very rare if a racquet cannot be strung two piece. A one piece pattern typically indicates that the mains end at the top. Most often, there will be more than one enlarged hole at the top, thus: yes, you can string a hybrid with no more extreme issues. Blocked holes may be an issue, but that is more a matter of racquet design rather than the pattern you choose to use.