On XDA, at times I see users requesting for boot partitions of a particular version of stock ROM and some people helping out by uploading and linking them.
I am not sure if it is a good practice, mainly because
a) it may contain sensitive information
b) it may create problems for the recipient, if they use it as John Wu creator of Magisk mentioned in the context of patching boot images
I searched around for answers, but no luck. To localize the problem consider that the question relates to devices with A/B Partitions, while a broader answer is welcome