I believe they’re using Geo DNS, and your traceroutes are all to the same IP. I suspect the networks in your traceroutes would get different answers for time.google.com - 216.239.35.8 and 216.239.35.12 seem to be outside the US.
I have graphs for time1/time2, from my home connection (cable modem). Client has a GPS PPS, so the offset movements are from the networks involved. You can see the response latency of time1 moving around, probably from Google changing their outbound path. There was one odd spike in time2 where the request latency went over 500ms. The most likely canidate of what caused that is the cable network, though.
NTP RTT, time1: min 27.9ms, avg 37.0ms, max 68.5ms, stddev 4.4
NTP RTT, time2: min 35.7ms, avg 43.2ms, max 75.1ms, stddev 4.2 (excluding the 547.7ms rtt)