Dialogs do not always respond to swipes to scroll content

Description

When a scrollable dialog (modal) is opened, it can be difficult to scroll the dialog's content. At times, the body element's overflowing content can interfere with dialog scroll, where swiping up/down controls the body content in the background instead of the dialog's content.

Step-by-step reproduction instructions

1. Add a Paragraph block.
2. Open the block inspector (settings).
3. Expand several sections so the block settings overflows the viewport.
4. Scroll to the bottom.
5. Wait a bit, then scroll down more.
6. Attempt to scroll upwards, occasionally pausing before beginning again.

Expected behaviour

Scrolling the block inspector is always responsive.

Actual behaviour

At times, it appears as though the block inspector does not scroll. In reality, the scrolling is occurring behind the block inspector in the body element where the block canvas is rendered.

Screenshots or screen recording (optional)

https://github.com/user-attachments/assets/d198a0a3-e035-4f57-8709-04adfe6f5853

WordPress information

• WordPress version: 6.7.1
• Gutenberg version: 20.0.0
• Are all plugins except Gutenberg deactivated? No
• Are you using a default theme (e.g. Twenty Twenty-One)? No

Device information

• Device: iPhone SE
• Operating system: 18.2.1
• WordPress app version: 25.7

Start by reproducing the issue in the block inspector with several sections expanded on the listed iPhone SE and iOS version. Compare swiping the dialog content with the body content behind it; this is done when repeated upward and downward swipes consistently scroll the inspector rather than the background body.