Mob spawning and block place prevention turned off by default?

[Onyxtite]

Hello! I was recently configuring the plugin and noticed that this two options were disabled by default: "prevent-block-place: false prevent-mob-spawn: false"

Do they negatively affect performance or generate any issues? I'd just assume that most people would use them otherwise, so it got me a little worried about activating them.

Could you confirm this isn't the case?

Thanks for your time!