The tech backlog just has to be justified among the technical contributors. Product is not involved at all. The only place where there may be some crossover is

The tech backlog just has to be justified among the technical contributors. Product is not involved at all. The only place where there may be some crossover is “architectural runway” which works to ensure that your future goals are possible on the system that you have. This could mean that if you know you’re going to have a need to scale a system based on a near-future feature request from product that you put the work into the tech backlog to get things ready in advance.