That may be your experience.... mine is different. The following is a graph from smokeping to Google and as seen, there is loss during peak times. This pattern was repeated consistently day after day.
I also have smokeping probes from the same source to other targets and saw no loss for those during this time.
The other point to consider is that Google uses Anycast DNS so the 8.8.8.8. address you're pinging is very likely to be a different physical server from the OP and me.
So whilst we may have a difference of opinions and experience with respect to ICMP response from Google, my point is that if the OP were to use TCP based "pings" then it removes throttling from the discussion completely
A Google DNS server is not going to throttle TCP requests to port 53.... or I'd like to think not.
Regards