OP reached a similar conclusion farther down in the Twitter thread:
facebookexternalhit/1.1 Facebot Twitterbot/1.0
What.
"This is the iMessages app's crawler [...] Apple has chosen to use this useragent in their iMessages app to ensure the unfurling of the URL and the rich preview works more often than not."²
Comments
OP reached a similar conclusion farther down in the Twitter thread:
facebookexternalhit/1.1 Facebot Twitterbot/1.0
What.
"This is the iMessages app's crawler [...] Apple has chosen to use this useragent in their iMessages app to ensure the unfurling of the URL and the rich preview works more often than not."²
² https://webmasters.stackexchange.com/a/138992