To keep it as short as possible: Have recently been using the 1.7 HBM, looked for a 1.22.2 port for a modpack, fantastic this looks great. Get to testing and see that the time to process the large nuclear detonations is drastically slower in this version, and really just want to know why or if there is any way to increase it, or just have it patched. The 'way' it damages the environment, at least for large hydrogen bombs, is also very different.

In 1.7 the average time it takes a Tsar detonation to complete on my machine without any additional mods is around 11-12 minutes, all the chunks will have finished updating by then bar some water oddities. In this 1.12.2 version under identical conditions it is taking upwards of 30-40 minutes and moves at a snails pace. Additionally the radius is not any bigger either, in fact in almost all cases the total destruction is significantly less. This is even noticeable with Schrabidium bombs where in 1.7 the destruction is near instant/real time whereas it feels slow and lethargic now.

A fix, or any advice on how to speed it up, would be greatly appreciated.

Sounds more like a hardware issue, could you provide details on your computer's parts? (Specifically, RAM & CPU)

Longest I waited for a Tsar to do it's damage was only 55 seconds, and that was on Windows. It took 10-20 seconds less on Linux.