Original quote in Polish: Pańskie oko konia tuczy.
This saying means that the business owner makes the business grow. It is said in a way to highlight the important role the founder or business owner plays in the business growth. It is when the business owner is looking after his own company, that the company grows and become more profitable.
In a way, this proverb is saying, that no one can replace the role the owner plays.
I think there are a lot of truth in this saying, this truth is that most employees do not put much dedication for the company. The person that puts the most dedication is the owner and sometimes the family. That explains why family companies have a higher success rate.
This also applies to tech companies, usually known as startups. The startup model usually consists of giving equity to most early employees, making them part owners. Hence these employees become really dedicated as if they were a family owned business.