There is some definite cross over as genres start to blend. Because you need to look much deeper than base mechanics, because Tales games have real time combat, and Shin Megami Tensei games, the main series at least have customization stats.
I think that despite the conventions normal for both JRPG's and WRPG's bleeding over in to one another region of origin still plays a key role in classifying each. Since the more story heavy nature of RPG's in general mans that they are more reflective of the culture of origin. But also certain subtle mechanics reflect this as well.
The first thing people mention when talking about both types is the difference in exploration style and level of freedom. As a culture Japan likes structure and that is reflected in their games as even "open world" games are just allowing some side exploration that eventually leads you to a single point where you advance, letting you find secrets along the way as a reward. Which is what Dark Souls does, it is more of a Metroidvania, than a true open world rpg which is really obvious since a big part of advancement is creating short cuts back to your central hub. Compared to something like Skyrim which is pure open world with little restriction allowing you to run off and have a worthwhile experience with he game for a long time while never touching the main quest.
Also theme wise and mechanics wise equipment is treated differently.
https://www.youtube.com/watch?v=os3lWIuGsXE EC has a great video comparing the culture behind how weapons and conflict are seen and how it related to games. To use a summary of what they eventually explain, Japan sees weapons as an extension of themself, while the West sees a weapon as a tool. So depending on where it came from you see a little more reverence of ones weapon in the game. A quick look reveals that barely any "loot" games come from Japan where moment to moment you are on the hunt for your next new weapon, most Jrpgs either stick you with one weapon type, or if you can use many weapons you are encouraged to find one you like and specialize in it. In most Jrpgs weapons are segregated by character, so every character has one weapon that they have made a part of them self, and new gear is rare and usually a product of hard work or general advancement in the main plot, or Dark Souls where the upgrading system encourages you to stick with a weapon you like and eventually make it better by adding a special effect to it or ascending it with a boss soul. Again compared to a western Rpg where any better weapon will be taken and the old one discarded.
Though to acknowledge Child of Light which cause the OP to start the discussion, from what I know you don't really have equipment in that game, at least in the Weapon and Armor sense traditionally so don't use that as an immediate counter to the weapon philosophy, as well as that exceptions exist, since sentimental attachment exists to weapons in many cultures.
I guess the TL;DR is, there are subtleties due to culture that are much deeper than what you can see on the surface so region of origin is still the best way to classify a Jrpg or a Wrpg despite how they may seem. Though an analysis could easily be a massive essay.
