你自己造的两个句子都有问题:
首先是,时态不对,要么he explained,要么he explains.当然在这里不是你的重点;
例句(2),感觉很别扭.在英语里,可以是:(a) he explains, "what i think is that." 或者 (b) What he explained, i think, is that. What都是引导主语从句.
原句:he complained [that {what you said was not true}] 的结构很清晰,that引导宾语从句,而what还是作从句里的主语成分.