Is the slightly rattling handle something to be concerned about?
I would mostly say NO, don't be concerned too much. It is a small issue of the Oyster 3 by Babystyle, and a similar one can be found on telescopic handlebars of other sofisticated prams (like a [[cybex-priam-3|Cybex Priam[[ - and it is not overly noisy on the Oyster.
The only time I would be concerned about this would be if you plan to use your stroller on heavy terrain very regularly. In that case, I would get something larger and sturdier because a lot of strain damages the joints of any stroller, and if the joint is on the looser side already, it just might get looser and noisier over time even more.
Overall, I really liked the Oyster 3 and for urban parents, it's quite a luxury pram & pushchair. Btw, here's our in-depth Oyster 3 expert stroller review to help you know more about this pram!
Here's an article about stroller handlebars to know more, if that helps as well 😉 And good luck!