Hello @jw27
External tools are specifically documented in the missing policy guide but not late, and I think thats because it is a bit of a grey area. It just depends on what the tool is going to pass over to Canvas. If it just passes a score then the late policy will not apply. But if there is a submission with timestamp then it might apply, and the late policy should deduct. There are many LTIs that are used for assignments and they all vary based on how it was created. I checked the Pearson page for LTI submissions with Canvas and they do not explicitly state it. Here is the Canvas guide:
How do I apply a Missing Submission policy in the ... - Instructure Community
The short answer is, you'll need to test it. I would reach out to the school and speak with someone and you could easily test this in a sandbox course. There is a good likelihood that Pearson MyLab would have scores apply to the late policy you have in the gradebook, but this is on an LTI by LTI basis and you will want to check it. IF anyone else has a concrete answer for Pearson MyLab, please feel free to post. You can also always contact Pearson and ask as this is technically their product:
https://support.pearson.com/getsupport/s/contactsupport
