Yes. On Oct 28, at least 33 addresses on TRON holding about $27M in USDT were blacklisted, with the largest holding about $7.8M, as reported via TrustSniffer and shared by WuBlockchain and _0xBenjamin.
The figures are balances at the time of flagging, not necessarily the exact amount frozen at execution.
No reason was given. Both posts say Tether has not publicly disclosed the reason, and TrustSniffer's tracker states it records the freeze action only and does not say who controls an address or why the issuer acted.
Tether's own @tether posts on Oct 28 only covered the FASE Foundation launch, with no mention of this freeze.