It's not unbelievable. It's just that they were SO BAD before he got here and this year the West is a mine field almost every night.
Here is that 20-game stretch:
L - Utah (88-111)
W - Orlando (112-103)
L - Toronto (106-112)
L - Detroit (113-120)
W - OKC (114-109)
W - BRK (130-116)
W - Okla City (126-121)
W - PHI (114-108)
L - WAS (124-125)
W - Phoenix (110-101)
L - New Orleans(77-100)
W - San Antonio (110-106)
W - Atlanta (113-97)
W - Miami (115-104)
L - MIL (90-93)
W - NYK (110-95)
W - MIN (112-100)
W - Lakers (97-81)
W - DEN (122-113)
W - HOU (117-110)
Wins against Bad Teams:
Orlando, Brooklyn, Philly, Phoenix, Knick, Timberwolves, Lakers
Middle Tier Wins:
OKC (2x), Atlanta (w/o Millsap), Miami, Denver
Wins against Good Teams:
San Antonio, Houston
Out of the 14 wins, with a team that has Dame/CJ, you should expect to win the 7 games against the scrubs, and 3 of 5 against the Middle Tier where only 2 of those teams (3 games) were Playoff teams....OKC a one-man team and ATL w/o Millsap.