Is it OK to take a shortcut in woodworking as long as nobody sees it in the final project? Absolutely.
I’m a big believer in taking shortcuts, mostly for practical reasons. My time is limited, so I try to take advantage of doing things more quickly and efficiently whenever possible. And while I may know a shortcut was taken, as long as you can’t see it (without resorting to ridiculous acrobatics) I just don’t have a problem with it.
In my current desk project, for example, I’m using a lot of stopped dados where the joinery is visible. However, there are a couple of spots on the undersides of things or that will be hidden by additional workpieces. For those, I saved time by doing through dados instead. Unless you turn the finished piece upside down or crane your head inside (which isn’t actually possible), you’ll never know they’re there. You might protest that this isn’t “how they used to do it.” You’d be wrong.
In helping my sister empty her old house, we got back a drop-leaf antique table we’d given her some 30 years ago. This is a small but very nice solid-oak table designed for small spaces, with a leaf on each side, which has been in my wife’s family for many years. I’ve never dated the table exactly, but my guess is that it’s early 20th-century.
To get it into my car I flipped it over to remove the legs, and discovered the builder had taken a shortcut when installing the hinges on the table leaves. Instead of mortising them in, the builder instead used a table saw to cut dados a bit longer than the hinges – they’re the exact width of the hinges, but about an inch longer, and you can clearly see the curve of the blade at the ends of the cuts.
The bottom line is that the hinges are effectively mortised in and work fine, but are invisible to anyone who doesn’t upend the table. In fact, this is probably the first time I’ve done so, which is why I’m only now discovering it.
It’s nice to know that my habit of taking logical shortcuts has an easily justified provenance.