Aravenel's check seems to ride the line, IMO. If the general rule is that you must go bigger than that for an SC, then the general rule would be saying that glen plaid is only OK if it's FU, which is bizarre.
The line between when glen plaid is OK for SC and when it's OK for suits, IMO, isn't as simple as whether or not the check is big. It's about whether or not the material itself is distinguishably not suiting. And this has more to do with texture, weave, and pattern than it does with just pattern alone.
Empty has a huge blown up glen check SC that's clearly not suiting, but if I remember correctly, it looks like a much rougher cloth. Even if the scale wasn't so blown up, I would think it's fine for an SC.
Really, what people should avoid is a very smooth worsted with a small glen plaid pattern, but this is kind of obvious. I also don't think Aravenel's material is decidedly one or the other either way.
But perhaps the most classic glen plaid suiting comes in the form of flannel. In fact, when you see flannel glen plaids they are always in suiting books, not books for jacketing . Aravenel's glen plaid appears to be worsted flannel. I cannot, for the life of me, imagine such a flannel being used for an odd jacket. My own glen plaid suit, made with cloth from the Harrisons worsted flannel suiting book, is both larger in scale and distinctly more wooly than what he's wearing, yet it is definitely suiting.
If you want glen plaid jacketing, it's probably going to be in the form of tweed. But even then, it could be intended for a country suit. So no, I don't think the distinction between suiting and jacketing appropriate glen plaid is obvious. Ninety-nine percent of the time you see a glen plaid, it is suit-only cloth. Sometimes it will work for a jacket, but the occasions are so rare, and the distinction is so hard to make without being familiar with what glen plaid suiting looks like, it is safer for beginners to avoid the idea of glen plaid jackets altogether.