If I am not wrong, ever since I have been living in Jurong for over
20 years, I have never come across a double decker 66 or 105.
Service 105 passes by a low bridge area (under CTE) upon entering
Lorong Chuan from Braddell Road towards Serangoon. That's why no
DDs were deployed.
In fact used to have NAC DDs on service
105 way back in 1991, until the route was diverted to
Lorong Chuan in 1992. After which all the DDs were withdrawn
and replaced with SD NAC MB0405s instead.