YES, it's RIGNHT, your N900 has only 2.5G connection means it is using EDGE connection, mine N900 is the same.

China Mobile's 3G network is based on TD-SCDMA techonlogy, which is not compatible with WCDMA. but their 2.5G/2G network is the standard EDGE/GSM.

if you want to use WCDMA/HSDPA in China, you can select another Telecommunication Service Provider, named China Unicom, their 3G/3.5G is WCDMA/HSDPA, fully supported by N900.