I'm also sort of getting a weird feeling uncertainty as to how the tiers are being considered. When the difference between OU and BL tier is based on usage and between BL and UU based on power, you basically say that anything you put into BL should be equal in power (but not in usage) to an OU. I would be fairly certain that we could find a pokemon who is too powerful for UU but not powerful enough to be considered an little-used OU (aka a BL).
No, you couldn't find such a Pokemon. We are not at all saying that all Pokemon in the BL tier are equal in power to all Pokemon in the OU tier. This is obviously incorrect, as no one could reasonably argue that even all OUs are equal in power. For instance, Tyranitar is generally more powerful than Aerodactyl (yes, I know they are different, but they're close enough). However, they are considered in the same tier of power, because the line of demarcation runs exactly between OU / BL and UU.
The tiers are not as quantized as you may believe, but rather, there are subtle gradations within each tier in terms of power. However, we draw that line by saying "This Pokemon would unbalance UU, regardless of how well it does in OU matches."
What he was saying is that there is no difference in power between OU and BL Pokemon as far as how the tiers are defined goes. If Salamence suddenly stopped being used for some strange reason, it would, in fact, drop to BL, because power has no role in determining that. The only difference between UU and BL is power. They both fall in the same range of how often they are used. Similarly, BL and OU Pokemon both fall in the same range of power (somewhere above UU).
Regardless, I don't think Linoone is quite fit for BL (remember, OUs people don't use) when something like Garchomp can Swords Dance once and achieve a slightly high attack stat while possessing better defenses, and without losing half its HP in the process and not being able to come in to do it again later when something goes wrong. Admittedly Garchomp doesn't have the Speed Linoone does after Salac and isn't 4x Ice weak, but it doesn't require setup from a team mate.
The performance of Pokemon in OU is irrelevant in deciding whether a Pokemon should be UU or BL. All that matters is whether the Pokemon is too powerful for UU. As much as Linoone / whatever is being discussed fanboys may hate this, we are not looking to keep any given Pokemon from being outclassed. If there were two Pokemon who were identical in every way, except one of them had 50 more base Attack and Special Attack (and would thus be superior in every situation), if the weaker Pokemon were still found to be too powerful for UU, then it would get bumped up to BL, even though that would relegate it to not being used on a competitive team, because it would still unbalance UU.