My advise on developing an understanding of a boat''s pointing capabilities was specifically aimed at developing a more detailed understanding of the pointing ability of a particular boat than one would necessarily expect to do at a sea trial. I had interpreted the question to be an owner of a new boat learning about the boat rather than during a sea trial. I agree with you that there is rarely adequate time during a sea trial to come to detailed conclusions about the pointing ability of a boat. That said, with a boat that is unusual in some way, it is not unreasonable to expect to spend the necessary time experimenting enough to get a general sense of the sailing ability of the boat.
My last boat purchase was a case of not following my own advice. In the case of the Farr 38 that I ended up buying, I had researched Farr 38''s sailing ability pretty extensively, and had sailed a sistership, and so had a reasonably accurate sense of their sailing ability. As things worked out I never did a sea trial on the boat that I eneded up buying(the boat was sitting in a field at a private residence in Maine unrigged and somewhat taken apart.) We did escrow funds to cover the condition of the engine, transmission, and electronics all of which turned out to be in good shape. There were a number of minor issues that came up once I had sailed the boat in terms of deck hardware in need of replacement but that was certainly within the rhelm of what I expected for a boat of the type, age and price range.