Apologies if someone else has already mentioned it, those are indeed coming from Amex as they don’t differentiate plastic cards from tokens in terms of transactions made and therefore notifications in your statements, including notifications and the transaction list within Samsung Pay, or any other Pay for that matter.
This is not coming from the Amex Pay app which you might or might not have installed on your device, it’s coming from the Amex backend system - and customers in general like it as it gives them real time alerts and control of all their Amex transactions, either offline or online.
What’s a bit unfortunate is that you also receive the pre-authorisations, e.g. £1.00 for Uber or Amazon or £0.10 for TfL, and many users don’t really know what that is and that the merchant won’t actually charge for that transaction.
I haven’t tried Monzo on Android Pay as I use Samsung Pay, I guess Android Pay would only give notifications for transactions made using your Monzo card token on Android Pay as this is how the connectivity between Monzo (or any other bank) and MDES should be implemented.