The Spaniard was relieved to keep the hard-fought match to just two sets ahead of her Saturday semi.
"I don't know a lot, but I know she's a young player and she plays really aggressive", Wang said.
The victory, in which she posted 33 winners to 21 unforced errors, will move the 102nd-ranked Yastremska to a new career high ranking in the top 80 when the next rankings are released on Monday.
"I felt like she had her A-game today", Gavrilova said.
The Ukrainian trailed Wang, from China, 6-2, 5-2 when the quarterfinal was suspended by rain on Friday.
The Hong Kong quarter-final was a rematch of August's US Open third round contest, which the Ukrainian won in straight sets, but here the tables were turned with Svitolina receiving a tennis masterclass from her opponent.
Minnesota 1 of 22 States Now Reporting Mysterious Paralyzing Illness
Officials said it's too early to know whether the total cases for 2018 will surpass those previous years. The cause is a mystery but the CDC and other officials have ruled out polio and West Nile virus.
British author becomes youngest to make Man Booker shortlist
And yet in every other respect they are remarkably diverse, exploring a multitude of subjects ranging across space and time. Every author who got to the shortlist will receive £ 2,500 and the victor will get the main prize of £ 50,000.
Le'Veon Bell not expected to report to Pittsburgh Steelers this week
That would put him out for almost half the season. "I still do want to go out there and win a Super Bowl with the Steelers". Bell has deployed a strategy that has kept Steelers officials and players in the dark, with no contact with any of them.
Wang, the world No. 24, grabbed headlines at the French Open with her straight-sets demolition of Venus Williams, offering a hint of what was to come, and later overcame Karolina Pliskova in both Beijing and Wuhan.
Svitolina is still in the running for one of the three remaining places at the WTA Finals in Singapore later this month and she now faces an anxious wait to see if a quarter-final finish will be enough to secure qualification.
Giorgi, who is seeking her second career title, improved to 3-0 lifetime against Van Uytvanck in reaching her second final at the event.
Next up for the Czech is second-seeded Frenchwoman Caroline Garcia, who beat Taiwanese No. 5 seed Su-Wei Hsieh 6-3, 6-4 in the other semifinal.
Wang, a semi finalist in Hong Kong previous year, faces former world number one Garbine Muguruza later Saturday for place in the final. She's now not entered, but could request a main draw wild card. "I went on court a little bit shaky, but after two games, it was OK".
It was the first title of the season for Garcia, who rallied from 1-5 down in the opening set tiebreak.