This is true for all encrypted traffic even Tor. But for LN it's especially revealing given the known message sizes and strict order of messages.

nostr:nprofile1qqszr7k0w6gclv3usnqmey68uzs6h2yt7dpw2dyeqt0sh8ehaxl8xyqpz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qz9thwden5te0v35hgar09ec82c30wfjkccte89v5nr has been using some padding methods + constant message sizes for covering its traffic for some time and nostr:nprofile1qqsdru78zcu6uwa6zlludjx7k87m8ft9q6e5jgsn6qe49rxzj9frwpqpz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qz9thwden5te0v35hgar09ec82c30wfjkcctehznuka just introduced an option for that too.