Route 53 accelerated recovery and CloudFront flat-rate plans

The statement "CloudFront flat-rate plans are not supported at this time" in the Route 53 accelerated recovery documentation means there's a specific incompatibility between these two features.

Based on the available information, here's what this means for your situation:

1. The incompatibility appears to be related to the integration between CloudFront flat-rate plans and Route 53 accelerated recovery, not specifically about having CloudFront distributions as alias targets in your Route 53 zones.

2. Your specific setup (Route 53 zones with alias records pointing to CloudFront flat-rate plan distributions, where the Route 53 zones themselves are not part of a CloudFront flat-rate plan) should be compatible with Route 53 accelerated recovery. You should be able to enable accelerated recovery on these zones without issues.

3. The limitation likely refers to Route 53 DNS services that are included as part of CloudFront flat-rate plans. CloudFront flat-rate plans bundle multiple AWS services including Route 53 DNS, AWS WAF, DDoS protection, and other features into a single monthly price with no overage charges.

4. While your current configuration should work, relying on Hyrum's Law (the observation that with a large enough user base, all observable behaviors will be depended on by somebody) would not be advisable. AWS explicitly states this feature combination is unsupported, so you shouldn't count on undocumented behavior continuing to work during an actual failover event.

There is no published timeline or estimate for when CloudFront flat-rate plans might be supported with Route 53 accelerated recovery.
Sources
Enabling accelerated recovery for managing public DNS records - Amazon Route 53
Key Features of a Content Delivery Network – Performance, Security – Amazon CloudFront
Amazon CloudFront CDN - Plans & Pricing - Try For Free