I don't quite understand what you mean here--could you clarify? In any case, while it's probably slightly safer to be on a direct flight where the same equipment is normally used, I've seen equipment substitutions done to get the second leg off, so you can still end up missing the second half of your flight even if it's normally operated by the same metal.

I agree with other posters that the purpose of these flights is to trick the customer into thinking that it's something that it's not. Back in the day you'd almost always see the same metal being used and there was a fairly strong guarantee that you'd have a seamless travel experience that just happened to have some take-offs and landings along the way, but in recent years it's all about (deceptive) marketing.