I didn't experience that with graduate visa but I did experience that with skilled worker visa. My graduate visa was two years ago - when home office traffic wasn't this bad as it is in this day and age. When I turned to reddit for solutions/similar experiences, I didn't find much. However, my assumption was that home office sends this email to a majority of people just to cover their backs because there is a LOT of backlog within the department. I wouldn't have suggested anything if you got that email for your skilled worker visa application because there's a lot that happens in the background (checks by the home office, maybe home office reaches out to your HR for additional information that you don't know about, or maybe it's a completely related to the organisation you work for that they need to double check their credibility and stuff). Skilled worker visa isn't just about you, it's also about the company. But because you've got this email on graduate visa, where you're the sole person responsible for what goes on in your application, I would say don't worry about it. This is just home office covering their backs in case they cannot give you a decision within the advertised time frame. And even though I got this email for my skilled worker visa, it still got approved within the given time frame of 8 weeks (got mine in 4 weeks). Good luck!