If a plan allows for hardships to be taken from other sources in addition to salary deferral (eg, match), do deferrals still need to cease for 6 months?

No.

I used to work w/ a plan that did this. Depends on:
1) What does the plan say? If it says all distributions under this paragraph get a suspension then you suspend.
2) What is your plan's source heirarchy? Does it provide for other sources to come out first? Then the answer is only if the w/drwl in question is big enough dips into deferals. If you're not taking deferrals then what you really have is a restricted in-service w/drwl.