If I saw "spoon", I'd assume that they meant "the actual spoon I use to eat cereal in my drawer" rather than either tsp or tbsp. The point is that the recipe author doesn't know what the right amount of that spice is. They can't know because the spice sitting in your cabinet is almost certainly much less fresh than what they have in the kitchen.

Spices tend to be flexible outside a few exceptions. I'd wager that you can just wildly change almost any spice amount in almost any recipe before you've ever made it and and have any sort of calibrated taste it'll turn out fine. Salt is a way bigger risk here and not many recipes give precise salt measurements.