Azure Stream Analytic at-least-once guarantees is not 100% accurate

Question

I have Azure Stream Analytic (ASA) that process data from the event hub as input.

And this job is for the finance biz so it is heavily based on Event Delivery Guarantees at least once of Azure Stream Analytic. But recently we found out that some data were not processed from the event hub and it leads to data becoming inconsistent.

The reliability of ASA can refer as below with 2 ponts:

1. Azure Stream Analytics guarantees exactly-once event processing and at-least-once delivery of events, so events are never lost.
2. Stream Analytics guarantees event processing with a 99.9% availability at a minute level of granularity.

https://learn.microsoft.com/en-us/azure/stream-analytics/stream-analytics-introduction#reliability

But when I asking support from the Microsoft team, a supporter from MINDTREE concluded that:

1)The probably cause of event loss is due to sudden outrage in backend issue from event hub side.  We would like to let you know that as this is a vast cloud platform and these kind of intermittent issues occurs once in a while but could happen which are very rare and our development team would be always working on improving the product to avoid such issues. Hence, the product gives 99.9% SLA for failures and at least-once concept as well, sharing the below document for your reference: https://learn.microsoft.com/en-us/azure/stream-analytics/streaming-technologies.

Is that statement correct? , as far as I know, SLA is for availability and we also have not come across any downtime information for ASA. Furthermore, during the same time frame as the missing data incident, there were a lot of successfully processed data.

And at-least-once guarantees are not 100% accurate is meanless, cause we can't rely on this service