Both 趨 (すう) and 勢 (せい) are standard on'yomi. 趨 means to tend towards, and 勢 means tendency. Incorrect readings like しゅんせい or しゅうせい mispronounce 趨. It refers to the general direction or tendency in which things are moving, describing a prevailing trend or current state of affairs.

趨 (すう) も 勢 (せい) も標準的な音読み。物事の動く方向や傾向を指します。社会や状況の全体的な流れを表す言葉です。