You can spectate ignited TNT in spectator mode probably because it's a entity but I think it's a bug because it does kick you out when it explodes unlike the creeper which takes a player to ignite or if a skeleton hits it
Linked issues
Comments 2
Thank you for your report!
We're tracking this issue in MC-47254, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki
-- I am a bot. This action was performed automatically! If you think it was incorrect, please notify us on Discord or Reddit
Duplicate of MC-47254, which was marked as Works as Intended. Spectating non-mob entities is considered a feature.