General description

When blocks are pushed by the piston at the exact time in the range TNT explosion, the blocks are destroyed but nothing drop. The expected behavior is that all destroyed blocks should drop as items since drop rate from TNT explosion is 100%. Moving blocks to reduce their blast resistance is a critical mechanic when designing TNT efficient blast chambers. Essential block farms such as cobblestone and wood rely on these, more so with the lack of TNT duping mechanic. 

Steps to recreate

Playing on Windows 11, version 1.21.23, on a creative default world. 9 figures are attached to illustrate the setup and problem.

• Step 1: Create a 9x9 obsidian platform, and at the center place an ancient debris (or any indestructible block). Go 7 blocks above the ancient debris block, place a dispenser pointing down, load it with TNT with a stone button on top. Create a redstone repeater and redstone line with 11 repeaters where 10 are set to 4 ticks and 1 is set to 2 ticks, powering an array of 5x2 piston pointing down, placed at the same Y-level as the dispenser. These are all illustrated in Figure 1 where smooth stone blocks are added to help counting blocks (not part of the contraption). The redstone line is shown in detail in Figure 2, the observer with 2 ticks is next to the reference gold block. Also note in this figure the configuration of crying obsidian to shield the pistons as well as aligning the dispensed TNT to drop right at the center of the ancient debris block. Then, the blocks to be destroyed by the TNT is a 5x2x7 volume of smooth stone blocks (or any movable blocks) to be placed directly under the array of pistons, as shown in Figure 3.
• Step 2: Sanity check. Temporarily remove the redstone line next to the diamond block so that the signal from the button will not reach the array of pistons as shown in Figure 4, and activate the button to dispense a TNT. Activating the button and waiting for the TNT to explode, observe that all destroyed blocks dropped as items as shown in Figure 5. This is consistent with the 100% drop rate from TNT explosions.
• Step 3: Place back the redstone line next to the diamond block as shown in Figure 6 and activate the button to dispense a TNT. After the explosion, many more smooth stone blocks are destroyed, yet nothing drops as shown in Figure 7. The experiment is repeated with ancient debris with similar results as shown in Figure 8 and Figure 9.