没有上下文很难确定咋回事，你这个句子是被替换过的，还好能找到原出处，有两处：

1.He thus conveyed the first principle of a successful apology. It must be direct.   You must never pretend to be doing something else in the name of apology. Some people apologise while leafing through a sheaf of correspondence or talking to a client. Sometimes, you will be obliged to apologise to a subordinate after blaming him for a mistake that turned out to be your fault. It is useless apologising to a hostess whose guest of honour you had insulted, by sending flowers the next day without mentioning your bad behaviour.

(引自https://www.sundayobserver.lk/2021/03/07/features/art-apology)

2.My mother thus conveyed the first principle of successful apology: it must be direct. You must never pretend to be doing something else. You do not leaf through a sheaf of correspondence while apologising to a subordinate after blaming her for a mistake that turned out to be your fault. You do not apologise to a hostess, whose guest of honour, you insulted, by sending flowers the next day without mentioning your bad behaviour.（引自“Proficiency in Reading Comprehension Simplifying the 'Passage' for you”一书第85页）

两处出处大同小异。对比你的原句，有两处替换，这下应该知道是什么意思了！that引导的是定语从句。