Does TH exemption carry into 401k plan rollover?

I've got a NFP that is terminating their 403b plan and starting up a 401k plan (for many reasons).  Most of the active participants are expected to roll their 403b plan balances into the new 401k plan.  Of course, we never had to worry about top heavy in the 403b plan... but what about these rollovers in the 401k plan?  It's the same entity sponsoring the plan, so they seem to be related rollovers, and they are participant-initiated.  But since they are from a 403b plan, do they retain the characteristic of not being subject to top heavy (so therefore I can treat them as non-related rollovers for the purpose of testing)?  Thanks.

I believe rollovers from related employer plans count in the Top Heavy calculation and as you know you will be using the account balance as the end of the first plan year since it is a new plan.