I never heard of a stem plant that needed a root tab to grow healthy.
There are no plants in our tanks that require or need root tabs. If you dosing the water column completely they are not needed to grow healthy plants. All you need to do is look at some of the tanks here on TPT that grow healthy plants in inert sand without root tabs.
If you not dosing the water column then yes they are helpful, otherwise most likely redundant and not necessary.
I don't have stems in my tank, I find them annoying nor do I use sand. That said, I have a crypt in my tank that has been there for almost a year. While it is green and healthy, it hasn't grown despite the fact that almost everything else has been while dosing the water column. If I give it some extra food at substrate level, one of two things is going to happen. I'm going to kill it which isn't likely or it will grow. I can say the same for my Amazon swords. Not a difficult plant that usually grows like a weed, mine have not.
I have tried to grow Vals 3 times and counting. While melting while in transition is normal, when I've tried them in the past with water column feeding alone, they die. Vals are heavy root feeders and just using ferts in the water column obviously didn't work. It is time to try something else.
I can look at pictures of tanks on here all day, that doesn't mean water parameters of all those tanks are the same. If you're willing to show me otherwise, I'll be more than happy to read and look.