There's no legal requirement for HRT letters, to visit a therapist, or how long anything should take. The WPATH SOC is a best practices document that some medical people follow, some say they do and don't, and others ignore. A doctor doesn't actually need a recommendation letter to prescribe you HRT, but they don't have to see you either - its up to them what their preference is. Not all therapists or doctors are actually any good either.
If you need/want therapy go for it, otherwise look at alternate options. Its going to vary very much depending where you are (or how much money you have). I chose to see a therapist for a year before I started, but it wasn't for letters. I found therapy helpful to clarify my thoughts, but I'm not asking permission of anybody.
Personally I'd try to find recommendations from trans people post for good doctors/therapists in your area. If you can't find any I'd suggest making a post asking, with the subject and location in the title so that people who might know are more likely to respond.
There's been posts in the forms before about red flags to watch out for in therapists and doctors. Worth reading.
