Hi, I don't believe that clause is new but it may be. We don't consider ourselves to be a "subscription service" either. Regardless, we have not had any of our customers banned or suspended for using our service. Obviously, of course, that's no guarantee of what could change in the future.
We don't use so-called "black hat" methods for view promotion like botnets or server farms or special software. If you have purchased views with us before, I'm sure the quality of your stats should indicate this.
Either way, in the past, we haven't had any problems. We don't have a crystal ball to read into the future. It's your YouTube account so obviously the risk/reward decision is yours to make.
I personally would consider it to be hypocritical and anti-competitive for YouTube to allow users to pay for promotion through their outrageously pricey "promoted videos" and then ban users for using a less expensive competitor. Furthermore, what if you didn't like someone else or their channel and you purchased promotion from a low-quality service provider for their channel/videos? How could someone prove that they didn't order those services themselves?
I think that banning users for suspected promotional activities would be an unfair and inflammatory move by YouTube/Google that would come at a very bad time as people start to become more and more wary of Google and its business practices. Users would likely catch on quickly and could start attacking each other's accounts by purchasing services for each other.
Of course, these decisions aren't mine to make. It hasn't happened in the past and I consider it unlikely to happen in the future. It's up to you to decide what to do.