scroll-behavior: smooth and element.scrollIntoView({ behavior: 'smooth' }) not working.

[OmeletWithoutEgg]

Version info:

Version info
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          |    ||    `^^`    ,^
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qutebrowser v2.5.4
Git commit: 294e73660 on master (2023-03-19 13:23:18 +1300)
Backend: QtWebEngine 6.4.3, based on Chromium 102.0.5005.177 (from api)
Qt: 6.4.3 (compiled 6.4.2)

CPython: 3.10.10
PyQt: 6.4.2

sip: no
colorama: no
jinja2: 3.1.2
pygments: 2.14.0
yaml: 6.0
adblock: 0.6.0
objc: no
PyQt6.QtWebEngineCore: 6.4.0
pdf.js: 3.4.120 (/usr/share/pdf.js/build/pdf.js)
sqlite: 3.41.1
QtNetwork SSL: OpenSSL 3.0.8 7 Feb 2023

Style: QFusionStyle
Platform plugin: xcb
OpenGL: Intel, 4.6 (Compatibility Profile) Mesa 22.3.6
Platform: Linux-6.2.7-arch1-1-x86_64-with-glibc2.37, 64bit
Linux distribution: Arch Linux (arch)
Frozen: False
Imported from /usr/lib/python3.10/site-packages/qutebrowser
Using Python from /usr/bin/python3
Qt library executable path: /usr/lib/qt6, data path: /usr/share/qt6

Paths:
cache: /home/user/.cache/qutebrowser
config: /home/user/.config/qutebrowser
data: /home/user/.local/share/qutebrowser
runtime: /run/user/1000/qutebrowser
system data: /usr/share/qutebrowser

Autoconfig loaded: yes
Config.py: /home/user/.config/qutebrowser/config.py has been loaded
Uptime: 0:16:24

Does the bug happen if you start with --temp-basedir?:
Yes.

Description
The CSS property scroll-behavior: smooth seems not working.
The expected effect is that when clicking some buttom or some anchor link, the page scrolls to a
certain element smoothly.
Now qutebrowser will directly jump to there.

The javascript function element.scrollIntoView({ behavior: 'smooth' }) is not scrolling smoothly, too.

I've tried chrome, firefox, falkon, only qutebrowser cannot scroll smooth.
I was expecting it to work after switching to QT6 as the Chromium version is very new.

How to reproduce

Here's some examples about smooth scrolling.

https://developer.mozilla.org/en-US/docs/Web/CSS/scroll-behavior
https://www.w3schools.com/howto/howto_css_smooth_scroll.asp