I think the big difference is that this year Microsoft knows Sony is not going to be at Gamescom.
When that announcement was made over a month ago, I'm sure a lot of thought was put into how to take advantage of that fact over at Microsoft. And if I were in their position, I'd have concluded the precise same thing: this is a chance to steal weeks of publicity for second tier games in our lineup that otherwise might get drowned out because they're not quite the biggest franchises or they're new untested IPs or whatever. It's a net win. They can say something silently about Sony's games lineup while simultaneously giving these games huge breathing room to catch the public's eye.
There's also the double bonus of giving the big announcements they're going to have at E3 even more room to breath.
The success of the strategy of course will depend on multiple factors. For example, if they took these games out of E3 and moved them to Gamescom and as a result their E3 conference seems starved due to it, that would make this move a bit more debatable from a positive/negative standpoint. But I am pretty sure that won't be the case. Another factor will be just how well received these games finally are at Gamescom. If they get a lot of people talking it'll be huge, but if there's any disappointment in there it'll make it seem like a squandered opportunity.
Ultimately, though, I think this was the smart move. If I were in their position, I'd have done this and perhaps even moved some more big titles to Gamescom too. It really is a huge opportunity for MS to capitalize on a odd strategic absence on Sony's part.