Not original
the oday trailer sailers (22, 23, and 25) all came with a spacer block. The purpose was to provide adequate space between the outboard and the transom, allowing full extension of the outboard tiller, to provide a more usable angle between the engine mount and the waterline, and to allow for the engine to be tilted or raised up without banging into the transom. On my Oday 23, I would not be able to fully extend the outboard tiller or tilt the engine out of the water without the spacer block.
The original spacer blocks were angled hunks of wood cored fiberglass, gel coated on the outside to match the hull. Yours is certainly not original to the boat. This is not surprising as this site has hosted numerous threads concerning repair or replacement of the original blocks. Given that the original spacer blocks were just about the same width as the engine brackets, I don't think they served as a load-spreading device, so there should be no structural reason why you can't mount the bracket directly to the transom. Just make sure your engine will go in the water on the angle you need, and that you can operate and store it without the block.