核心问题
One new model has lately been developed for business people.
《最新高级英汉词典》(商务印书馆, p.625) 认为 lately 不能用于肯定句。据此, 我认为上面的句子有误。请看该词典的论述: “[辨异]lately 与 recently 含义相同。前者用于否定句或疑问句, 后者用于肯定句, 例如: I have seen him quite recently (a short time ago). 我最近(不久前)看见过他。”
词典解答
lately 不仅用于否定句中,亦可用于肯定句中; recently 不仅用于肯定句中,亦可用于否定句中:
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I've been unwell lately. (= recently) (OGEG) 近来我身体不大好。
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I have not been sleeping well (CGEL) 我近来一直睡眠不好。
由此可见，《高中英语教科书》中的句子并没有什么错误，更详细的情形，见 recently。
lately/late 见 late
lately/recently 见 recently