Thanks for citing your sources, I think your source may be out if date, though! The “free init time hack” was killed in August (unless I’m missing something - never used it myself).
Good callout that it's no longer free. However, you still get extra CPU, and assuming your execution environment isn't reloaded, that init time is amortized across all the invocations for the execution environment.
SnapStart is more widely available, which is the other option for shrinking the billed time spent in init (when I left, only Java SnapStart was available)
https://aws.amazon.com/blogs/compute/aws-lambda-standardizes...