I'm getting a blocky stepwise pattern when I look at the flow in my conduit using the SWMM solver, but my pattern was set up as a continuous smooth pattern.
This can happen if your pattern is set up with a full range of whole number hour increments. (see below article for more details) When a pattern is set up this way, it will be exported to the SWMM solver as a "time pattern", in which case it is handled as stepwise.
So, one way to resolve this and treat the pattern as continuous is to alter one or more of the times in your pattern so that it is no longer a whole number. For example change the one hour row to 1.01 hours or 61 minutes. In this case, the program will export the load as a "time series", which is treated like a hydrograph and thus no longer "stepwise".
Pattern load handling with the Explicit (SWMM) solver