Keep in mind that the goal of that category right now isn't to find perfect switch-ins to everything. It's to have something to throw in front of a threat so that it can't just spam its STABs all over you and punch huge holes in your team for little risk. Sometimes that's really all a team needs to play around a certain threat since momentum and offensive pressure will generally do the rest of the work. Yeah, something could hit you on the switch with a coverage move, but that's less likely since it's riskier to spam a weaker coverage move on switches than to spam a strong STAB move. The mere existence of such a conditional switch-in puts the opponent under pressure, forcing them to go from things like, "Cool, I can just spam Landorus's Earth Power and cause massive damage every time," to, "Do I click Earth Power and risk giving Latios a free switch, or do I go for Knock Off and risk letting Keldeo come in easily?" That little bit of breathing room can make an enormous difference. Besides, if I were to just limit switch-ins to things that switch in perfectly safely, then there'd be few if any Pokemon listed under some threats (think things like Landorus and Kyurem-B), implying that these Pokemon are nearly impossible to switch into at all when in practice that's not true.
I'll go ahead and clarify this one last time. As long as a Pokemon can switch into a threat's STABs somewhat comfortably and win, I'll count it as a switch-in. Eventually, I do plan on splitting the current SI category into perfect switch-ins and conditional switch-ins (which will give me a lot of room for "grey area" checks), but it'll be a while before I have time to do that. For now, that's the definition I'm using.
