I'm sorry but I just did a S rank. my LS found it. We were there from the start. 5 seals (full party). All hitting it non stop entire fight from the start.

This system is a total joke. And incredibly unfair and luck-based.

I've done 5 or 6 S ranks, many of which my LS spawned today, and have yet to get full credit for any of them (always 30 or less), regardless of full party. Each fight mob kept disappearing.