Trackpad support on iPad does not work well. When scrolling with your finger, scrolling up shows the tab/URL bar as expected, but when using the trackpad, scrolling up with two fingers fails to pull the bar down. This makes the bar inaccessible when using just the keyboard and trackpad, and means I have to either lift my hand off the keyboard in order to scroll by touch just to access the bar, or else do something like hit Command-T to open a new tab and then Command-W to close it again, just to prompt the bar to appear. Scrolling should be consistent between touch and trackpad, and not block access to something as critical as the navigation for the entire browser.
No, I believe this to be a bug. Pulling down with a finger shows the URL/tab bar, pulling down with the trackpad does not, making it basically impossible to access the URL/tab bar without having to touch the screen. It's very frustrating, and it's clear the behavior is supposed to work the same way, it just doesn't track the cursor the way it tracks your finger.
It's extremely easy to replicate this and understand the frustration. Grab an iPad with Magic Keyboard, and use only the keyboard and trackpad without touching the screen. Open a site with a long page and scroll down using the trackpad so the URL/tab bar hides itself. Now try and scroll back up with the trackpad to expose the URL/tab bar. It's very difficult to trigger, if at all. But touch the screen with your finger to scroll up and it'll appear immediately.