Why does `await asyncio.create_task()` behave different then when assigning it to a variable?

Question

Why is there a different how tasks are run between tasks 1-3 and 4-6 in the code below?

Code:

import asyncio


async def do_something(i, sleep):  # No I/O here
    print("Doing... ", end="")
    print(await no_io_1(i, sleep))


async def no_io_1(i, sleep):  # No I/O here
    return await no_io_2(i, sleep)


async def no_io_2(i, sleep):  # No I/O here
    return await io(i, sleep)


async def io(i, sleep):
    await asyncio.sleep(sleep)  # Finally some I/O
    # t = asyncio.create_task(asyncio.sleep(sleep))
    # await t
    return i


async def main():
    await asyncio.create_task(do_something(1, sleep=4))
    await asyncio.create_task(do_something(2, sleep=3))
    await asyncio.create_task(do_something(3, sleep=2))

    t4 = asyncio.create_task(do_something(4, sleep=4))
    t5 = asyncio.create_task(do_something(5, sleep=3))
    t6 = asyncio.create_task(do_something(6, sleep=2))
    await t4
    await t5
    await t6

asyncio.run(main())
print("\r\nBye!")

Output:

Doing... 1
Doing... 2
Doing... 3
Doing... Doing... Doing... 6
5
4