Is this really a 100% Sativa?

First of garden of green isn’t reputable IMO. Seen lots of questionable shit from them. Buy from a breeder in the future - not a seed broker /reseller. Anyhow - no it’s likely a hybrid honestly. But the whole idea of sativa and indica are just kinda categories of traits. It’s not like you can do a DNA test to see how much sativa is in it - cuz it’s not technically a quantifiable thing. I don’t know what strain you’ve got but most stuff on the market are polyhybrids.. if you want what I would call a true sativa - find some landrace seeds with long flowering times and those thin fingered fan leaves. A lot of these companies breed with other varieties to get more favorable results for home growers. For example - Durban poison I’ve grown from ILGM has been obviously bred with some shorter flowering time and stouter genetics. This is common with Durban apparently from the mainstream seed companies. I touched on it before but I see you’re a new grower - I’d recommend finding a breeder that actually is doing the work and breeding and then selling those seeds. Most the companies advertised on here are just middle men, brokers, selling “white label” seeds. Bred by another entity, shipped to them and then slapped with that companies label. I could go on for some time on breeding and what not but you get the point. Personally, I’m partial to ETHOS for most my seeds.