That wasn't your homework you did there, but you get the prize anyway! :wink:
You're right that MS didn't explicitly state their planned release cadence for phones, but if it's intended to be similar to the W10 insider preview for PC's, then MS are aiming for about one insider preview per month. Some builds will occasionally take longer.
If the latest build is not even a month old, how in the world are MS slow? You're right. They just aren't.
@AnkitGondalia
Coordinating the tasks of thousands of engineers, all of whom work on a code base which shares many components between xbox, PCs, servers, phones and IoT devices (MS must ensure that changes to xbox don't break phones etc) while ensuring that the development process leads to one build per month that can be released to a software illiterate public, is no small feat!
If you've ever worked in a project of that size and complexity you'll know it's not comparable to peeling potatoes.