Tiff export broken?

Hi all!

Exported compressed tiff files (lzw or zip) in C1 have nearly double the file size (or at least are significantly larger) as tiff files exported from Lightroom, with same settings:

Input: Canon Raw
Output: tiff, full res, sRGB, no layers, no editing, no resizing, no cropping, no output sharpening, no meta data

How is that possbile? Is this a bug?

Thanks!