In the context of ADHD hyperfocus doesn't necessarily equate to special interest.
So it can absolutely be games on your phone.
What they look for in assessments is whether these bouts of hyperfocus or special interests are restrictive. Think along the lines of "just one more episode and then I'll go to bed/take the laundry out/wash the dishes". This can then spiral into other areas of poor time management and display not being able to start tasks and not being able to finish tasks.
There's a lot of information about there about intense hyperfocus around hobbies and things of interest, which is common because of how the ADHD brain works. It craves novelty and interest, but some people lean more towards urgency and challenge. These people might not be able to switch off from work mode, or home mode, because the challenge and urgency are far greater than the interest and novelty of the tasks around them. For these people it can impact relationships, because you're not able to fully engage with those around you and it creates this issue with a mismatch in task prioritisation.
You also don't necessarily need to be particularly knowledgeable about a topic for it to be a hyperfocus or special interest, it just needs to meet the criteria of restrictive or repetitive.
Some people with ADHD might have these micro-hyperfocuses. For example people who hobby switch. You sink a bomb on supplies, materials, resources and then you get bored of it half way through and no matter how you try to push through you'd have more luck forcing yourself to hold your hand on an open flame and burning yourself than you would finishing your task.
I'm sure everybody has felt some sort of task inertia which feeds into the "everybody does that" mantra some people feel, but if you're experiencing this often, and it's causing chaos around you, appointments are getting missed, shopping isn't getting done, the house is falling into ruin, or you're just not able to keep on top of your work load because you can't pull yourself away from what you're doing it would fall under the executive dysfunction umbrella of not being able to finish and start tasks.
Equally if you've ever seen something that needs doing then while you're doing it you see something else so you decide that you need to do that first so you make a start, then you find something is missing so you go to the shop to buy supplies and then while you're at the shop you see something for another task you've been meaning to do so you pick that up and when you get home you start working on that and forget completely about the other 2 tasks you've already started, then that can be a display of how hyperfocus works on novelty and how a sense of urgency whether relatively urgent or not can play a part in how you internally prioritise tasks which can be restrictive and detrimental.
There's a good about this and it's a perfect visual representation of how scatterbrained you can get with a hyperactive mind even if your body isn't particularly hyperactive.