I share your doubts regarding the DSTROBE signal. It's not used according to ATA spec in the design and I don't understand what it's intended for. Furthermore, DSTROBE is definitely not needed in PIOMODE cause it's an UDMA signal.
Apart from this special point, you didn't tell how you operated the HDDs, so there's nothing to comment. I suppose, the drives can operate in PIO mode. Not keeping the necessary ATA command timing may be a reason for failure with certain devices because of individual timing differences.
