None of the major cloud vendors actually hit 99.99% uptime.
None of them even promise that -- last time I checked, it was 99.95% for most of them.
(To my knowledge, it's the only AWS service to promise 100%.)
The question is whether the guarantee is meaningful by way of whether the penalties will significantly dissuade failures to meet the guarantee, and I'd argue in the case of Cloudflare, this isn't the case.
[Edit: Cloudflare's standard] penalty is a service credit defined as follows:
> 6.1 For any and each Outage Period during a monthly billing period the Company will provide as a Service Credit an amount calculated as follows: Service Credit = (Outage Period minutes * Affected Customer Ratio) ÷ Scheduled Availability minutes
https://www.cloudflare.com/business-sla/
And that's woefully inadequate for any enterprise client with mission- or life-critical services.
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TL;DR: A SLA is a guarantee, by the very definition of the word "guarantee," that a service will be delivered to a specific level and that certain agreed-upon penalties will be applied to the service provider if this guarantee is not met.
Edited for tone.