Very simple to recreate bug.

• TNT is an opaque block, according to the Minecraft wiki (In it's unprimed state)
• Opaque blocks in Minecraft are known to stop the passage of redstone unless undermined by a repeater
• Despite no repeater present, the redstone signal is passed on.

STEPS TO RECREATE: Follow the screenshots provided

THINGS TO CONSIDER:

• It does not matter whether you place the TNT before or after activating the lever:
• The redstone is cut visually
• The cut off redstone is powered
• Despite the dust being on, TNT is not primed
• In picture 5, the "powered" dust is successfully transmitting power to the green wool block, suggesting this is not just a visual glitch. - - The fact that power from the dust is capable of powering other things, supports the point about TNT not being primed