From DMARC RFC 7489, 6.3, emphasis is mine:
ri
: Interval requested between aggregate reports (plain-text 32-bit
unsigned integer; OPTIONAL; default is 86400
). Indicates a request
to Receivers to generate aggregate reports separated by no more than
the requested number of seconds. DMARC implementations MUST be able
to provide daily reports and SHOULD be able to provide hourly reports
when requested. However, anything other than a daily report is
understood to be accommodated on a best- effort basis.
This suggests that the normal interval for reports is 24 hours and a shorter period can be requested, but is optional. It mentions nothing about a longer interval, and a longer interval would also mean the receiving mail system should cache the data for extended periods.
This is why it's perfectly fine that Gmail has chosen to simplify this and send daily reports. A hint of this can be found at G Suite Admin Help About DMARC:
DMARC reports
You can set up DMARC to send you a daily report from all participating
email providers.
This makes me believe Gmail doesn't care about the ri
tag at all.