(Some but not all) terminal emulators are capable of rendering CJK perfectly aligned with Latin even when mixing fonts. Browsers are fundamentally incapable of that because aligning characters in different fonts wasn’t a goal at all. VS Code being a webview under the hood means it inherited this fundamental incapability.* Therefore, don’t hold your breath.

* I'm talking about the DOM route, not <canvas> obviously. VS Code is powere by Monaco, which is DOM-based, not canvas-based. You can "Developer: Toggle Developer Tools" to see the DOM structure under the hood.

** I should further qualify my statement as browsers are fundamentally incapable of this if you use native text node rendering. I have built a perfectly monospace mixed CJK and Latin interface myself by wrapping each full width character in a separate span. Not exactly a performance-oriented solution. Also IIRC Safari doesn’t handle lengths in fractional pixels very well.