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In some maps, the use of bugs is implied, but it's unclear in which ones, as this isn't stated in the map title (except for something like Bug Race :). And what's left is to ask Marlo, like a living encyclopedia, who has completed a good half of the hardcore maps?) Honestly, understanding this fact has significantly reduced my motivation to complete maps.
There aren't many maps where bugs are required, even among the Chinese ones. Mostly, bugs are needed in small puzzle maps. So, at least in HL, you can play any map without hesitation; I haven't observed any bug exploitation there.