Can a 4x4x2 Wye fitting be used on a horizontal section of a 4" drain waste to tie-in a 2" tub drain? Or should a san-tee be used?

I'd like to be able to come into the 4" waste line at a 45 degree angle, as opposed to 90, but I thought I read somewhere on here that a wye could only be used on vertical drain stacks. (searched for the thread but couldn't "re-find" it).

Any help would be appreciated.