I use a Deans "Ultra-Plug" as an arming device. It does make a small spark when plugged in. So, looking at the ESC, it has some hefty capacitors, which are apparently connected across the battery input. When power is first applied, these capacitors are uncharged, and initially represent a zero-impedance load to the battery, with no resistance in the circuit to limit initial charging current. The current spike is high, but of short duration.
Deans connectors are gold plated, so are highly resistant to arcing damage. I can find no deterioration on these after many operations.