Yeah, but wasn't something particularly long.
But the reason is clear: Rocks, Roger and Garp are all dead or old, and in Garp's case we have already seen how he fights. There is no secret or reason to not show them. In fact, it's now or never probably, since they all have had their FB at this point.
On the opposite, Loki is clearly going to be showcased in the present. Even his fruit was kept secret; how could Oda have showed the fight in these conditions? He has lwasy done that when the FB was about a character that was going to be used in the present.
Remember Kaido vs Oden lol? Oda didn'r even show the hybrid and the fight was only two hits. It's the same.
To me it don't matter if Oda show Loki full form while fighting harald since he would just regen and story would have to be the same way .
Like i said the story aspect of how the fight were done and what they mean in story were differnt to compare them on a power scale level.
Grap and Roger beat DR rocks and get him back to normal and he get kill by HK .
Loki vs harald was harald getting back to his sense after fighting loki and letting his son kill him without doing anything
It not the same thing for the simple fact that rocks never got back to his sense during that fight where harald did .
Plus there was no saving harald so he had to died where with DR you can save people but rocks get kill after by others
The fact that you can save people from DR going to be very important because shit load people on elbaf are in DR and oda not going kill them off.