Ya I get that he’s talking about retroactively apply what would be reasonable on the setting but aren’t you (and every one else) doing the same thing but to the show?
Like all of us thinking Glad would/could have drown is us retroactively applying real world logic and saying “well it'd be reasonable in Show to” even though we are never shown any thing to actually fit it.
Or even with Tolkiens work as you said he wrote a story about an elf who is never heard of again in the sea and pretty much every ones respond is “well it would be reasonable for him to have drown” even though Tolkien ever actually wrote about him drowning just him not being seen again which could have numerous other outcomes.