Two (byte) buffers are equal if their contents are equal.
However, currently, BufferData comparison (PartialEq) uses its capacity as part of the comparison. Therefore, two slices are considered different even when their content is the same but the corresponding BufferData has a different capacity.
Since this equality is used by Buffer's equality, which is used by all our arrays, currently arrays are different when their contents are the same but the underlying capacity is different. I am not sure that this is what we want.