Picture anything built in layers, with a position marked somewhere up the stack: floors in a building, ranks in an office, numbers on a scale, in a game. High-level puts the mark near the top. What changes from sentence to sentence is only which stack you are standing in — and one useful side effect of standing high is that you see the outline of everything and none of the small parts.
From the word’s history
Wiktionary gives the formation plainly: high + level. Level carries the idea of a layer or a height, and high places you near the top of it.
Wiktionary 記的組成很直白：high 加 level。level 本身帶著「一層」或「高度」的概念，high 則把你的位置放在那一疊的上面。這也說明了為什麼同一個字可以講樓層、職級、數值和遊戲等級——換的只是那一疊是什麼。
Wiktionary entry 'high-level' (packet evidence), etymology_text: 'From high + level.' — source_ref kaikki:3f6f69a190036ae4:1167174489
登入就可以看每一支怎麼連回核心畫面。