Like Ringo says, 10s are reasonably nice anniversaries to celebrate. They don't have to do anything, but it's always nice. This is particularly highlighted with them mentioning it in adverts for the Thorpe Annual Pass.
Furthermore, with other parks celebrating anniversaries as a common thing (Efteling, Disney push their 5 year anniversaries, Towers have done stuff for Nemesis and Oblivion), it can lead to public demand for anniversary celebrations.
I mean, we know they've mentioned VR will be there, and there'll be some upcharge features. VR gaming isn't that common, and the upcharge stuff almost definitely won't be stuff available to play at home. And retro games (probably stuff like Pacman arcade machines from the 80s) aren't common in homes. So I wouldn't read too much into it.
I think some of the questions being raised are fair. This is being pushed as a big thing, when at best, it should be a side addition to expand the line up. And the worth of that sort of event when the park needs to improve its offering and get more people in in the first place is questionable. Then also why people would go to Thorpe for this when there's hundreds of locations they can do this.
Oh, and that the first comment from Thorpe shows how childish their social media feels. 'We're saying it will be great so shut up'