After running Analyze -> Against Auto Generated Timing Analysis Report,
io_pad_i path tracing control is disabled. Run the same report
with the same path tracing control enabled, and the second report is
missing the OFFSET IN constraint.
If you run a report with the path tracing controls disabled, then re-run
the report with the same path tracing controls enabled, some of the delays
will be lost. The workaround is to re-load the design in Timing Analyzer
each time the path tracing controls are changed.
This will be addressed in a future release of the software.