A team of Learning Designers, Support personnel, and product advocacy team members at Moodle US took a deeper look at client concerns with guest access user activity experiences, and noted the following:

• All guests are prompted to resume lessons even if it is their first encounter. This is what initiated the concern.
• SCORMs are also limited with a guest experience.
• While feedback can be submitted as a guest, you cannot link someone directly to the questions area of feedback.
• Guests may receive alerts that activities have already been attempted.
• There are likely other activities that have guest access limitations and quirks.

It would appear that similar issues were reported a long time ago in https://tracker.moodle.org/browse/MDL-12100 but it was closed due to the version chosen. We can confirm this behavior still exists today.

The team who looked at this problem together felt it worthy enough to request a more thorough look at the guest user journey. We also noted that the guest user seems to always be ID=1, and perhaps this is the reason why Moodle feels the guest has already "been on the site."