More like someone processing your next visa application getting automatically collected data on your previous visits from all kinds of sources public and private and seeing that you lied about your visit the last time.

What sources would keep track of foreigners doing private business meetings and conferences?

Some of this is also a question of "do you want to take the risk of having an indelible black mark in your travel history?"

As an example, the US asks for your travel history (where you went and why) and a list of your social media accounts. It would be trivial to correlate a conference related social media post with a stated reason of tourism and flat that.

They might not do this, but I certainly would not want to jeopardise all future travel for that if.

Social media posts (not just from yourself but other attendees), credit card purchases, license plate scanners, the conference itself publishing the list of attendees etc. If someone you have not told knows where you had been then the government can know too. It's not guaranteed but the risk is unacceptable to some.

Clearview[1] is not shy about selling its facial recognition services to government agencies and continues to scrape social media for photographs. It is within the realm of possibility that the foreign service officer who issues visas may query a Clearview product for photos of a visa applicant, and get a detailed picture about their activities at a conference while they were on a tourist visa.

1. https://www.clearview.ai/

In Russia, the FSB monitors all attendees of conferences. If you attend a conference in Russia while on a tourist visa, the police will come up to you and force you to sign a police report that you have done wrong, and possibly pay a fine. I know that from firsthand experience. I would imagine that the situation is similar in China, Vietnam, Egypt, and other authoritarian states.