That may be, but the claim that BitArrays are generally slow and only to be used when one is memory constrained is inaccurate. BitArrays are very fast for some use cases, and less so for others.
This would be a fun project — I’d bet you could get a really efficient BitArray*Array matmul implementation.
BitMatrix this seems like it should be extremely convenient. since you can pack 8x more data into registers.
It is also practically useful. E.g. for one-hot encoding categorical data.
In any case
BitArray is nice for purely binary data.
It is described in the video, if I remember correctly.
it is described in the video at the time stamp I linked to