What this 8-position MTA-100 header is for
The 3-644456-8: This is a single-row, unshrouded header from TE's MTA-100 series, designed for board-to-cable/wire connections where you need a simple, cost-effective interconnect for general-purpose equipment.
Current, voltage, and temperature — the operating envelope
Current rating is listed as varies by wire gauge — in the MTA-100 system, the limiting factor is the crimp terminal and the wire size, not the header pin itself.
That exposed pin length is what the mating receptacle grabs onto.