The big question is what are you looking for or hoping to find? Because outside of some specific scenarios like schooled, actively feeding fish...Most of the time scanning is done looking for cover/structure, presence of baitfish, or just get general lay of the land in the areas you're fishing....IE, most of the time it's not actually a situation where if you find what you're looking for you're going to immediately catch a winning stringer.
I generally don't do much scanning on an actual tournament day...Here and there sure, but really only to check or confirm something I already know about, like scanning across a point to see if it has what I'm looking for (bait or fish or other activity) for a single pass before dropping the trolling motor on it. It's very rare that I go out and scan/scout for new stuff on a tournament day itself. Most scanning can be done anytime beforehand...Whether its immediately before the event or not. I spend most of the winter scouting and scanning at places that I'll fish tournaments on the next season. Structure, topography, and most cover (besides grass) doesn't change...So you can find it in December and put it to work in May .
Also, club level stuff is almost always just a single day (occasionally 2)...So you can't really compare that to practice for a 4 day pro level event, it's almost apples vs oranges. You need a lot of stuff to support 4 days of tournament fishing, so when you see the pros talking about scanning for so long in practice it's because they need at least 4x as much stuff. They need to account for the 4 days plus factoring in other pros finding the same stuff they did. Most of the time they aren't locals either, so they need familiarize themselves with the place as well.
One day events can usually be supported on a single 'milk run', so the strategy for that relies more on your experience on the specific lake/river and what your backlog of successful areas/patterns is like. Even with zero practice you can put together successful single day tournaments if you have enough experience/history on that body of water. If you are fishing mostly local/club one day tournaments, a very good strategy is to focus on building up your own milk run for each place you fish...Whether that's deep, shallow, or a mix is up to your personal style and the types of waters you fish. Scanning is a big part of all that, but not really on the tournament day itself .