Even if they had been referring to an (obviously absent) pass-through outlet there, which would actually make a tad
more sense
, it's still weird. The pass-through current wouldn't be limited to 1.5A — it would be the current rating of the power cord, which could be from 5A (the rating of the fuses provided with some British units that made their way into my {yes,
huge} stash) to 10A (with 1mm² conductors), or even 15A in North America (with 14AWG wire — but most of them, predictably, use 18AWG which is about 0.82mm²), minus the current drawn by the PSU itself. (A built-in mains switch could impose a limit below that of the connector, but even then I would expect it to hold to at least 6A.)
Why would they go to the expense of the extra "filter" board and not put any EMI filtering on the main PCB, anyway?