You have an interesting theory, so I decided to check his matches of his stream today and his stream yesterday.

Yesterday's stream
Eevee's starting SR: 4503

• Game 1 (Nepal)
  Average SR: 3950 vs. 3946
  Eevee loses
  Goes to 4474 SR (-29)

• Game 2 (Horizon Lunar Colony)
  Average SR: 4029 vs. 3951
  Eevee wins
  Goes to 4498 SR (+24)

• Game 3 (King's Row)
  Average SR: 4098 vs. 4139
  Eevee wins
  Goes to 4517 SR (+19)

• Game 4 (Watchpoint: Gibraltar)
  Average SR: 4016 vs. 3941
  Eevee wins
  Goes to 4531 SR (+14)

• Game 5 (Temple of Anubis)
  Average SR: 4103 vs. 4079
  Eevee wins
  Goes to 4545 (+14)

Eevee then switches to an unranked account, so I can't keep tracking anything. I already spent too long on this so I'm not checking his 2 day old stream. :\

Record: 4-1
Net gain: +42

Today's stream
Eevee's starting SR: 4587

• Game 1 (Hanamura)
  Average SR: 3903 vs. 3728
  Eevee wins
  Goes to 4597 SR (+10)

• Game 2 (Watchpoint: Gibraltar)
  Average SR: 3851 vs. 3858
  Eevee loses
  Goes to 4580 SR (-17)

• Game 3 (Ilios)
  Average SR: 3904 vs. 3972
  Eevee loses
  Goes to 4564 SR (-16)

• Game 4 (Volskaya Industries)
  Average SR: 4034 vs. 4053
  Eevee loses
  Goes to 4544 SR (-20)

• Game 5 (Numbani)
  Average SR: 4113 vs. 4058
  Eevee wins
  Goes to 4557 SR (+17)

• Game 6 (Watchpoint: Gibraltar)
  Average SR: 4111 vs. 3866
  Eevee wins
  Goes to 4568 SR (+11)

• Game 7 (Eichenwalde)
  Average SR: 4241 vs. (4 GMs, 1 Master & an unranked w/ a top 500 player icon)
  Eevee wins Goes to 4585 (+17)

Record: 4-3
Net gain: -2

My conclusion:

Two of his three wins today were in games where his team was the big SR overdog, which is obviously going to give him lower SR gains. Other than this, his losses and gains seem relatively similar. Regardless, Eevee's statement in OP's post is exaggerated.