Right, but the weird thing was that grand parent got a full trace up to the target and I didn't as usual. By experimenting a bit I found that when sending UDP

Right, but the weird thing was that grand parent got a full trace up to the target and I didn't as usual. By experimenting a bit I found that when sending UDP packets the traceroute is incomplete, but when sending ICMP also my traceroute is complete. Explains how the grandparent could present a full traceroute. I had just taken it as a fact that full traceroutes are rarely possible these days. For reasons like you say, it's overhead for them and they don't want you to do it.