Yeah I even had Yates on the list == DUH!!!
How does Froome winning the 2017 Vuelta predate Thomas winning the 2018 Tour?
2018 Giro - last GT Froome won
2018 Tour - Thomas
2018 Vuelta - Yates
2019 Giro - Carapaz
2019 Tour - Bernal
2019 Vuelta - Roglič
Even if you want to get cute and include Froome winning the 2011 Vuelta, that was a) announced in July, so would break the streak before Bernal, and b) it made the 2011 Vuelta Froome's first GT win, so in theory would make it 6.
EDIT: I'm in my 70th year, sometimes I get confused