There have been other forms of Samsung tablet users who also do not have dark mode yet. Only thing I can think of is that is due to some ui optimisation from the larger screen of the tablet, as the settings option itself appears differently to the phone version along with some other things, (appears as pop up in centre of screen rather than using up entire screen like it is on phone.
I have also uninstalled cleared data and cache and re installed on my pixel 3xl setup app identically to tab s7 and the option is there. Same google play account and same Microsoft accounts. Please help me resolve this issue as this app is essential to me and I've been told I can't use this app for extended periods of time with my eyes, my current only solution is to use a colour inverter in accessibly options which breaks a plethora of elements.