Figure out why the new flex-grow attribute doesn't work on some blocks

[jessica-townsend]

Background

We've noticed that on some blocks, the flex-grow attribute doesn't appear on the frontend. We need to investigate where this happens and why. There are a few possibilities:

• Inside a query loop block
• On image blocks
• On blocks that already have a style attribute

[jessica-townsend]

It seems like the issue here is when the flex-grow attribute is used on post-x blocks. Examples include the post-title, post-featured-image, post-author, etc. It might be because the output for these blocks is changed in the render callback function: https://github.com/WordPress/gutenberg/blob/trunk/packages/block-library/src/post-title/index.php#L19

I can look into this further, we might have to use the render block hook instead to filter the block content server-side