You can save even more space by using an actual codec for unity plugin and the correct lz4 library.
Tick verbose mode and set up unity plugin without any level settings. This way you can see what level you should use. Nowadays unity bundle assets using lz4hc with level 12 mostly.
Code:
15:55:29 - Selected ARC/DS method for Data1a-01.bin was: xtool:munity,lz4hc,l12:lz4_193:dd3+4x4:b64mb:lzma:ultra:64m:bt4:fb273:lc8:mc1000000
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16:01:46 - Overall input size: 4.04 GB
16:01:46 - Overall output size: 2.57 GB (Ratio 63.62%)
16:01:46 - Overall conversion time: 00:06:15
PS: Nothing is ripped.