I'm with you on that one Carpenter. I'd be very much against the cabinet connectors, and I presume they suggested using them without glue. These connectors do the job they were intended for well, but they will only provide a clamping force in one plane. They were designed to hold two pieces of worktop together at a joint, but only where both pieces are supported vertically by attachments to the surrounding walls.
The biscuits will do the same, and probably better job than the dowels. As Carpenter says, all the strength here is going to come from the glue bond. Get a good glue bond and it will be stronger than the wood. I saw a piece on 'This Old House' where a timber frame manufacturer was testing glue joints on lengths of stock finger jointed together to form structural components. These were placed in a machine which pulled them apart with increasing pressure until they gave way, not once did the glue joint fail.
OhPincy, you could use some [broken link removed] if you can't get your hands on sash cramps. Protect the edges and corners of the worktop though. Also make sure the pieces remain alligned as you apply pressure. To ensure this, you could use a couple pairs of 2x3 or similar. Put one on each face, and use a G clamp on each end, if you know what I mean.
Leo