I have the exact same issue. Working with Metabox AIO and Oxygen. With post_fields included in the shortcode, conditional logic works fine but as soon as I remove it (or remove "content" and leave "title") it just stops working, displaying the field all the time.
Here's the shortcode used in Oxygen: [mb_frontend_form id="command-form"]
I'll contact Oxygen team to see if they can provide help. In the meantime, would there be a way to make it work (for example, keeping post_fields="title, content" in the shortcode but disabling it via CSS display: none)? -- I've tried this but couldn't get it working.
The issue has been resolved by Oxygen team. The problem was caused by Oxygen's built-in optimisation "Disable WP Emojis", which needs to be unchecked in Oxygen --> settings --> Bloat Eliminator. Conditional Logic now works fine!