Blinking cursor in NSTextField causes drawRect: to be called in custom NSView

Question

I'm running into the strangest issue:

I have a Cocoa app with a custom NSView inside an NSScrollView.

When I click into the text field, drawRect: is called on my custom view each time the cursor blinks.

If I move my custom view outside of the scroll view, the issue goes away. Also if I place my test view at the very bottom of its parent view, the issue goes away.

This is not a duplicate of Why does the blinking cursor in textfield cause drawRect to be called?, it's the same issue, but I did not override hitTest:. In fact, my test view implementation looks like this:

class TestView:NSView
{
    override func draw(_ dirtyRect: NSRect) {
        NSColor.red.set()
        dirtyRect.fill()

        logWarning("drawRect in custom view called. dirty rect: \(NSStringFromRect(dirtyRect))")
    }
}

My view hierarchy:

NSWindow
  NSSplitView
    NSView
      NSVisualEffectView
        NSTabView
          NSView
            NSScrollView
              NSView
                TestView

It seems to be a combination of the NSVisualEffectView and NSScrollView. I can't reproduce this in a fresh project. I tried reshuffling views in my existing app, but I can't pin this down.

The issue in action:

Note how drawRect: is called as soon as the text field has focus and stops when I click outside. I don't see why an unrelated view has to be redrawn with each caret pulse.