It's actually been this way for some time. It changed back when they allowed multiple project files to be opened at the same time. And yea, it's easy to be suddenly in the wrong project file. But if you're working in old-style stand-alone projects, you have to actually close the project you're working in to get that to close if you only want the new project open.
I've moved on to the Productions mode though, even as a one-person shop. All my projects for the year are organized inside the overall Productions folder setup, with subfolders for each segment of my business, and within those, individual projects. I love working in Productions, it means I've got all my b-roll, audio, everything for the whole year available quickly in any project.
And without ever duplicating assets, besides opening and working in the projects faster.
Neil