Proves nothing since his sage mode is fodder so he absorbs less anyway his rasengan was as small as nardos big ball rasengan.
Also stamina doesnt equal chakra Orochimaru used many techs and summonings and his stamina is 3.5.
And proof of the fact his chakra is non existant is he transported a kyubi ball followed by summoning and transporting kyubi he was gassed.
- Suppressing the nine tails throughout Kushina's entire labour. Do you know how many hours labour lasts?
- Minato used FTG approximately 13 times the night of Kurama's attack
- 1 S/T barrier to transport a massive Tailed Beast Bomb - the bigger the attack the more chakra
- 1 Rasengan
- 1 Giant Toad summoning (this takes a lot of chakra)
- Teleports both Kurama and a Tailed Beast Bomb at the same time - both large things which require a lot of chakra
- Uses the Reaper Death Seal to seal half of Kurama within himself
- Then the 4 contract Seal
- Summons yet another toad (Geretora)
- Summons the alter where he place Naruto
- Then seals the remaining Kurama into Naruto before at last dying
Yep, Minato has low stamina

You people are morons. Who's denying manga facts now, the scan clearly says you cannot manage nature chakra unless you already possess enormous chakra inside of you... FACT!