The fact that you are worried about this is very telling that the advertising industry has been doing its job of selling product successfully. However, it is totally unnecessary to have separate fertilizers for every genre of plants.

Your tomato plants as well as anything else you might be growing will be fine with the so called cactus fertilizer.

My only concern is that the directions for application might be off.

Cacti and succulents tend to be light feeders, so I imagine the fertilizer is fairly weak. It should be fine. But there's no need to fertilize tiny tomato plants that have just started growing unless they're showing signs of nutrient deficiency.

LOL, I use whatever fertilizer I have on hand. Most times I use tomato for anything that flowers or has fruit and sometimes just the plain 10-10-10 for the jungle plants. I usually always make it 1/2 strength.

IF tomato starts/seedlings need to be fertilized, it should be at a highly diluted rate. I don't fertilize starts at all unless they show signs of nutrient deficiency, which only happens if I leave them in their starter cells too long. When they go in the ground (I no longer bother to pot them up unless the weather is too cold for plant out and they're really stressed in the starter cells), I give them one dose of something with N like fish fertilizer or mix in a little granular balanced all-purpose fertilizer into the planting hole, and then I don't fertilize again until they start flowering and setting fruit, at which point, I start regular light fertilization with a formula for fruiting veg or tomatoes. Nothing needs to be tomato specific, but just because tomato formula is easy to find, I just use it for all my fruiting veg once they get to the flowering/fruiting stage. For plants that do well with more N, I just supplement the fruiting/tomato fertilizer with something cheap and readily available like fish fertilizer.

Thanks for the comments! I’m a total newb to gardening. My tomatoes are my first edible to grow besides just basic herbs and lettuce. I panicked lol. They seem to be doing great.