Row block: setting dimensions width as fixed in only one child block produces wrong results

[burnuser]

Description

Entering Fixed Width in only one paragraph (of two or more) in a row block produces strange results (much smaller, than entered), but never the expected.
It seems to work when both (all) paragraphs in the row block get a certain fixed value, but not when only one child block gets a fixed value and the others remain as Fit

Step-by-step reproduction instructions

1. Insert two paragraphs (longer than editor width)
2. Convert/combine paragraphs in a row block
3. Select one of the two paragraphs and change Dimensions - WIDTH to Fixed
4. Enter a value, e.g. 200px (or 50%)
5. Leave the other paragraph as Fit
6. Check the resulting webpage => No 200px (or 50%)

Screenshots, screen recording, code snippet

Example with 200px in first paragraph:

Example with 50% in first paragraph:

Environment info

WP 6.5 + Gutenberg 18.7.1 (but also without Gutenberg)
Twenty Twenty-Four (also with Twenty Twenty-Two)

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes