TMX import with double context matches
When you created your TM without context enabled, and you import a TMX into your TM, all context fields are ignored on import.
When you import a TMX with the traditional context matching (the Simple context option when you create a TM), then the ID-based context is taken into account.
When you import a TMX into a TM where you have the double context option chosen,
•then a missing text flow context is interpreted as a "no segment",
•and a missing ID-based context is interpreted as an empty string ID.
If you have a TM with double context and the context ID is null in the TM and in the segment to look up, you get a 101% match, if the preceding and the following segments both match.
If you have a TM with double context and the context ID is equal in the TM and in the segment to look up, but the text flow context is different, you also get a 101% match.