Tbf, if the current spoilers are legit this chapter inevitably evaporates most of the hype behind Xebec's Marijoa admiral encounter.
If old and injured Gaban is in the general level of power as GV Xebec (not saying that this version Gaban is actually equal to Xebec obviously), then old Rayleigh or old Gaban in healthy states should be extreme-diff, either way material for Xebec. That would place Xebec at absolute best on equal footing with someone like Kizaru. Not even that, arguably.
So that admiral 25yo Xebec (should be noticeably weaker than his GV self) killed was either a complete bum or had unfavourable factors against him.