Exactly. This question was answering in TNG. Scotty revealed himself to be a lazy baffoon.
No no no. He simply took the needed amount of time needed to get something done (x), multiplied it by a factor of 4 (I think it was 4..), then said it would normally take that long, but
he could do it in x.
If you read the books, after Mr. Scott arrives in the future in that TNG episode, he goes back to starfleet and goes into starship design. He designed most of the Soverign class (1701-E) if I remember correctly.