It's more than likely one of two things:
The announce done in your client is more recent than the last time the site has scraped that particular torrent (IE your client is more up to date) OR, you're seeing clients that are DHT only, which won't be shown on the tracker (because they're unauthenticated).
Either way, it's nothing to worry about. Qbittorrent respects the private flag in the torrrents so it won't seed to unauthenticated peers, some clients don't which results in some "leakage" for lack of a better word.
Also, you needn't worry about not connecting to leechers - it's probable that those leeches are already connected to enough peers to saturate their download speed so there's no need for them to actually connect to you. With all that said though, thank you! It's always cool to see people giving back via seeding, it really does have a huge effect. As an example, when the new BADIK release launched, apart from the first 10 minutes, we actually didn't see all that much traffic from our servers afterwards - the torrents were so well seeded. I was a little disappointed tbh, I kinda wanted to stresstest our network a bit lol. Reminds me of this:
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