[Bug]: Annual Site Stats Insights Reporting Wrong Posts Number

### Quick summary

Annual insights are reporting a wrong number of published posts per year on a user's site.

### Steps to reproduce

1. Check 4929036-zen
2. Go to https://wordpress.com/stats/day/annualstats/ for the specific site
3. Notice the difference and small number shown there.

### What you expected to happen

Show an accurate number of posts published each year.

### What actually happened

Annual site stats are showing a very small number of published posts per year, compared to the real number.

Start by reproducing the discrepancy for site 4929036-zen at the annual stats page and compare its displayed yearly totals with the site's actual published posts. Trace the annual stats reporting path in the Jetpack repository, then verify that each year's displayed count matches the posts published that year.

Written by the indexing model from the issue text.