I have done plenty of patios this way including my own 10 years ago which is still standing now , using blobs of mortar helps bed the slab easier and once the slab is compressed onto the blobs it pretty much fills the area of the slab especially on a slab this size, there certainly would not be any area of the slab that could crack due to not enough mortar but will agree that on bigger slabs then a full bed is needed but we all have our own ways of laying slabs. thanks for your comment.