“Your keyboard may occasionally capture ‘snippets’ of your typing. This includes short phrases, plus data about the keypresses you made to type the words, and whether you deleted or changed anything. These snippets are captured anonymously and you do not need to be signed in to share them.”

https://support.microsoft.com/en-gb/topic/microsoft-swiftkey-keyboard-sharing-your-typing-data-faq-d737059d-8810-448e-b376-9af56171a37d#:~:text=If you are signed in,separate Microsoft product improvement service. From Microsoft themselves