Depends your perspective. I you are looking for a quick exit, trade for trade drags it out because of the limitations on liquidity. If manipulation is what you are hoping for trade for trade pretty much eliminates that possibility. Normally it is done to allow for the neat and orderly exit of investors hoping to recoup some of their capital from a security that is under SEC investigation for fraud. In fact in my years of trading and investing I have never seen it done with a pink for any other reason.
At the moment there is a chance, maybe as good as 50/50, that this is not a normal trade for trade restriction and it is being done to enable the determination of the true O/S for the execution of the merger. But don't get your hopes up. First off, consider the company GRDO is keeping.
Monday morning Watson may choose to explain why it was done. If not, then it will be up to investors to find out for themselves.