求助：美国经加拿大转机回北京，到底是否需要转机签证？

想订加行的机票从Seattle-Vancouver-Beijing-Vancouver-Seattle的往返票，中途不出Vancouver机场，仅停留2-3小时左右。郁闷的是看不懂以下这段英文：
National China (People's Rep.) (CN)
Embarkation U.S.A. (US) /Transit Canada (CA)
Destination China (People's Rep.) (CN)
ALSO CHECK DESTINATION INFORMATION BELOW

Canada (CA)

Visa required, except for :
- holders of Hong Kong (SAR China) passports.
TWOV (Transit Without Visa):
Visa required, except for Nationals of China (People's Rep.),
(only if holding China (People's Rep.) passports) are allowed
to transit without visa via Vancouver International Airport
(YVR) to/from the U.S.A. provided:
- arriving on a direct, non-stop flight from: Beijing,
Guangzhou, Hong Kong, Shanghai, Manila or Taipei; and
- being ticketed to arrive at YVR only with the following
carriers: Cathay Pacific, China Airlines and Philippine
Airlines; and
- holding confirmed onward tickets within 24 hours of arrival;
and
- not leaving the transit area (no overnight facilities
available); and
- transiting to their final destination;
关键就是：
and
- being ticketed to arrive at YVR only with the following
carriers: Cathay Pacific, China Airlines and Philippine
Airlines;
而我选择的是加行或者国航，这么说是不是肯定要转机签证？（另外国泰哪有北京上海广州直飞温哥华的航班啊！这个条款是否很白痴啊！
想节约300USD看来不容易啊。）
请问坛子里有谁能给出准确的答案？多谢啦。