你可以把 more so than 看作是固定搭配，也可以不看作固定搭配，因为其实它也可以作进一步分析：so 是替代前面出现过的形容词或类似形容词的词。2020全国卷1中的这个 so 用于替代前文的of particular interest，即：

The far side of the moon is of particular interest to scientists because it has a lot of deep craters (环形山), more of particular interest than the familiar near side.

又如：

She feels relaxed here, even more so than at home. 她在这里感到很放松，比在家还要放松。

He’s quite bright—well, certainly more so than his brother. 他很聪明——嗯，比他弟弟还要聪明。

Of all the careless people no one is more so than Bill. 在所有粗心的人当中，没有一个比比尔更粗心的了。

The choir sang sweetly, and none more so than the Welsh boy. 唱诗班唱得很悦耳，尤其是没人比得上那个威尔士男孩儿。

再如下面的句子也属于类似情况，so 代替的是前面提到的情况：

Many people are concerned about education, but nowhere more so than in France. 很多人都关心教育，但没有任何一个地方比法国更甚。

There has always been an interest in genetic cloning, but never more so than in recent years. 基因克隆向来引人关注，近年来更是如此。