i dont know is this allowed or not, but the sword frog sheath remind me of goblin slayer sheath from goblin slayer manga and anime.
basically its a universal scabbard or sheath where you can carry any type of sword or weapon especially when the other sword dont have it sheath or scabbard (usually from looting), because you cant use the same scabbard or sheath that your previous sword use because it maybe to long, to short, to big, to small, or different shape for your original scabbard/sheath to fit in perfectly and will hinder movement.
like when your weapon stuck or break and you loot enemy weapon to use, maybe because its far better than your original weapon, or because you really need new replacement right there right now because its better than nothing, or just a new backup or loot/prize weapon to the frog sheath for ease of carry while you still carry your weapon in hand, while still not safe from many enemy or monster in the wild or far from civilization or blacksmith to fix it or create the new scabbard/sheath. outside of price, you far better to use new weapon rather than fix your cheap adventurer sword anyway, its different if its godly sword though but if it already achieve godly level i doubt it can break, or dulled,or chipped even after numerous use, or its a sword made of good quality steel that unlikely for adventurer or murderhobo to get again.
iam sure you already know, the cons is it wont protect from the element for iron or steel base weapons, so this type of sheath is more for disposable or cheap weapon (that doesnt have their own scabbard or sheath) or to carry the good loot weapon for a while until perfect sheath or scabbard is ready, and dangerous to person behind the wielder, unable to ride horse since the point can accidentally cut or pierce the horse rear when riding.
oh yeah, also i assume this is more specifically for carry around your hip type rather than the back sheath/scabbard right? because if it include as the back scabbard/sheath thats another story, which i think you know already.
(i want to put image regarding goblin slayer, but its pretty much copyright material and this site is very against it, so i can only suggest you to read the manga to get what i mean, iam not recommend the animation because it look ugly and i dont watch it to know is it show it or not, at least skip to chapter 2 it already show it, chapter 1 is very NSFW and irrelevant to your question, and a reason from another manga name "goblin slayer year one" chapter 18 when he try to sheath enemy goblin sword to his scabbard and it not fit well during his early carer. the guy change weapon alot because common weapon is not indestructible and he face multiple opponent at once so no time to pull out weapon that got stuck inside the enemy body or the sword get slippery from the blood and fat, so he just loot enemy weapon right away to use.)