So, since that's the way it works and it does give more possibilities, I simply:
1. Deselect all and drag out as PDF
2. drop into a new document and drag out as TIFF
Lossless, but confusing. Why should the image well work differently in different formats? It seems to me that every non-Create format should give you the same stuff (within what they support -- so JPEGs would never have transparency like PNGs do, but otherwise the dimensions of the resulting image would be the same). You're the boss, of course, but that's my take.