你的理解是对的。the whole 后面通常不可以接不可数名词的，但 the whole time 是个例外。请看来自柯林斯英语语法系列《限定词及数量词》的说明：

更多例句如：

He had remained alert the whole time. 他始终保持着警惕。

I went for a run there, keeping an eye on the children the whole time. 我去那里跑步，其间始终留意着孩子们。

I can't work with people breathing down my neck the whole time. 要是旁边总有人紧盯着，我没办法工作。

We enjoyed the party, but he sat there the whole time doing nothing and saying nothing. 我们在晚会上玩得很开心，但他却一直坐在那里，什么也不做，什么话也不说。

We thought that he disliked her, while the whole time [=all along, all the time] he was in love with her. 我们以为他不喜欢她，然而他一直都爱着她。