This has to do with the code base the tracker uses. Some simply do not send that info to your client.
I don't know which code base is which but you'll notice all trackers that use the format
/announce.php?passkey= (eg RevTT)
will not return any seed/peer information to the client (with one exception I have noticed, where they append additional information after the passkey). Anything using the format
//announce (eg TL)
will return the seed/peer information. Either code base could be reconfigured to send, or not send the details I'm guessing, but it is enabled by default in that second code base.
I think Gazelle and TBDev the two most common code bases used on trackers? Now to figure out which one is which.
Edit: Just did a search and see there is now TS-SE, FTS and BtiT code bases, not sure if they're modifications to a base Gazelle or TBDev or stand alone systems or if they send seed/peer info.
Q