Does boss reward drop chance scale with World Tier in Genshin Impact?

I am farming the Cryo Regisvine for character ascension materials. I have beaten it twice at WL4, boss level 62, and got two drops of Shivada Jade Fragment when I want to get Shivada Jade Chunk.

I have gone up to WL5 and beaten the boss at lv72, and still only gotten Shivada Jade Fragment.

It was my understanding that the higher the level of the boss, the more likely it would be to drop the better materials, but this seems to not be the case.

What are the drop chances of items from bosses? If I need items which can drop from the boss at WL4, am I better off farming at the lower world tier to make the fights easier and thus farm quicker for the materials I need?

Regarding the drop rates table I'll link a traveler.gg spreadsheet that has aggregated drop data for reference. The sample size is pretty low across the board especially at lower world levels so it is hard to tell how much if any difference exists between the average amount of a given ascension material between world levels. My (unsupported mind you) reading of the data is that if a given ascension material can drop at a given world level it drops some amount in a range (0-x) that is the same for all world levels. Despite that there is clear reason to always fight the highest world level version possible, each successive world level adds to the pool of things that can drop which may not necessarily relate to the ascension materials. At world levels 2, 4 and 6 the next tier of ascension material is added to the possible drop pool, 4* chunks are added to the pool at WL4 and 5* gemstones will not be added until WL6. At WL5 specifically 5* artifacts are added to the drop pool and you are guaranteed at least one 4* artifact. Do take note that the odds of a 4* chunk dropping isn't very high no matter the WL and even when 5* gemstones are added at WL6 the odds are pretty abysmal and variance makes it hard to gauge the intended average drop rates.

I'd recommend against fighting bosses at a lower world level if you can help it because the main limiting factor (hopefully) isn't time but resin.