hmm he means that because when more than 1 card effect takes place, a chain occurs.
The general rule is, when a chain occurs, the card that activates last would have its effects resolved first,meaning that when the monster effect takes place and u chain skill drain to it, skill drain is activated last, meaning that skill drain's effect is resolved on the chain first, negating the monster effect.
Hope i explained it correctly.
On another note:
However, except for jinzo, as jinzo effect negates traps effects, you will have to activate skill drain first (meaning it shld alrdy be faced up on the field before jinzo is summoned), otherwise u cannot chain skill drain to negate jinzo's effects.
If skill drain is alrdy face up, then jinzo's effects would be negated =)