MIRI implements mosaics with larger pointing offsets for each tile than are available for dithering.
Overview of MIRI mosaics
Mosaics with JWST using MIRI are accomplished with larger pointing offsets for each tile than are available for MIRI dithering; however, a dither pattern may be executed at each mosaic pointing. MIRI-specific mosaic patterns can be implemented using the Astronomer's Proposal Tool (APT). In general, mosaics are defined with some overlap to provide full coverage, but this is not a requirement.
Dithers and mosaics are distinct in terms of operational ordering and, therefore, the resulting overheads. All dither positions must be executed before filter changes are executed. All filter changes are executed before proceeding to the next tile in a mosaic.