Understand the superblock error

I know this is a common error, but trying the solutions proposed in other threads hasn't fixed yet the issue. Furthermore I want to understand what I'm doing.

This is what I did:

1. downloaded an RPi image
2. made the image file bigger using truncate
3. mounted the image file as loop device
4. deleted and recreated the rootfs partition at the same offset (but bigger)
5. created a third partition in the empty space
6. re-mounted the resized partition as loop device
7. resized using e2fsck and resize2fs
8. dd to the SD card

Well, at point 7 I can still successfully mount all partitions with their own offset as fdisk says.

But once on the SD card I can't mount the resized partition, I get the error:

bad geometry: block count 1966848 exceeds size of device (1572864 blocks)

Any attempt to execute e2fsck to that partition will fail. fdisk shows the size of that partition is 12582912 sectors, that is 1572864 blocks, on both SD card and img file.

As far as I understand, the problem is the partition table tells something but the actual content is different.

I'm wondering when I could have done something wrong - I mean in which passage. I followed the procedure twice with the same result.

I don't need to save the data on the partition, but I also wonder if I can fix this without restart from scratch.