Not exactly. Li-Ion's are not accepting same current due whole charging process. Basically, nominal "C" value of charge (for example, 1C) is only happening during ~half of charging process. Then, battery is "reporting" ~4.2 V, and charger starts to gradually decrease current, keeping battery at no more than 4.2 V (less in case of N900, as it's charging and using power at the same time), during so-called "saturation" stage. BTW, the higher initial current, the faster "saturation" charge happens. This sole fact defeat purpose of charging LiIon's to full with more than ~0.8C, as time saving is negligible (due to longer saturation phase).

OTOH, there is method called "fast charging". Basic principle of it, is to charge only as long, as time/power ratio is optimal (i.e., only to about 70%-80% of maximal capacity). This way, we benefit from using higher initial current, thus charge time decrease dramatically. Of course, drawback here, is that we don't use full potential of battery, but it have added benefit of extending overall battery life (Li-Ions lifetime benefit from keeping it between 20%-80% of State of Charge [SoC] - this is how they're used in "heavy duty" environments, like electric trains, where cost of replacing huge battery's arrays is higher, than benefits from charging them to 100%).
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As for Your discovery about fake charger - it explains mysterious 650 mA max. How lame, 50% of declared max current

/Estel