The 30" max distance from the standpipe is not a concern, only 18-20" is needed.
The not less than 30" from top of standpipe to trap weir is a bit of a wildcard. Everything is behind drywall so I don't know exactly placement of the trap. Measuring on the wall, the top of standpipe is 34' above concrete slab. Subtract out 1.5" for sill plate and it would be max of 32.5". I put a tape measure down the standpipe and it starts bottoms out right 31". It seems like the bottom of the trap is just above the sill plate. Not know what the specific trap depth is for the standpipe using 2-4" range, the current height from top of standpipe to trap weir seems like it could be anywhere in the range of 27-30".
The top of laundry try is 34.5" from the slab, which is 1/2" below the current top of the standpipe at 34", so standpipe has to be extended to meet code from that aspect alone.
The washer outlet box is being replaced as part of this work and there is room to move it vertical, allowing standpipe to be extended. How much the pipe can be extended depends on the exact outlet box that it used as there is a receptacle a few inches above the box. Looking at dimensions of various outlet boxes and their faceplates, the standpipe should be able to be extended 2-4.5" inches.
Chances are high that the not less than 30" inches from top of standpipe to trap weir can be met without issue.
Assuming all the requirements are met, is there anything undesirable about this method? Most of the posts around here suggest avoiding it. The last plumber who was here said the only downside was you would hear the washer water draining through the utility sink drain, but you already hear it draining through the top of the standpipe. He didn't have anything else to add other than the more "correct" way would be to tie the sink into the vent stack so it could be separately trapped.
