You may still be hurting yourself more than you hurt them. I say may since I don't know your circumstances, but I am missing out on communications from my employer since they insist upon using WhatsApp.
I agree since they should not be using WhatsApp for internal communications. The problem is that they do not see it that way since it adds additional hurdles with respect to communications from their perspective. That is especially true since I am the only holdout and few people seem to know how to use the organization's email system with any degree of proficiency.
It's too easy to do and can be done from quite far away. Also you don't need eyes. An innocent pic or video taken in public can capture that info.
I think long ago, Signal used to display phone number just beneath name when you are chatting someone. That always made me a bit uncomfortable. Now they don't do that, only displays name.
If they are that close.. they can see the words you are writing. If you are sending winky love icons who you are sending it to may not be as important your actual content.