Thank you folks! Let me clarify the question a little bit. I know many people enjoy blogging and vlogging every detail of their build. I'm not one of them. There are many people much more qualified than I am to educate the world about building planes, and I'm not looking to join this cohort. So really I'd like to keep logging to a minimum - the less meta-work I do the more time I have for doing actual work. I went through FAA and EAA (thank you Sean) and found that requirements are very loosely defined. It's good to know that "time spent building" is not mandatory - I purposely avoid tracking hours. But also the EAA interpretation is outdated and IMHO misleading.
On the page about builders log, the EAA says "FAA guidance (FAA Order 8130.2F, Chg. 4) recommends that pictures be included in your builder records. Lots of pictures are a plus, especially pictures showing you actually working on the project."
In fact, FAA order 8130.2F has been superseded long time ago, and the current version is 8130.2J, but also the FAA order mentions no such thing about photos. The only place the word "photo" appears in a relevant context in the order says "Examples of documentation include ... A comprehensive builder’s log that includes items such as drawings, engineering specifications, plans, references, handbooks, kit manufacturer’s data, photographs, video, documentation of commercial assistance, yada-yada". So per FAA, photographs are listed next to video and kit manufacturer's data, and emphasizing photos is just EAA's creative interpretation of the letter.
I understand that people are talking from their positive experience obtaining airworthiness and repairman certificates, and I appreciate that. Keeping an extensive log with photos or videos of myself building would be on a safe side and will satisfy FAA. But given that I've already build a chunk of the empennage with no logs, I need to find out what is the bare minimum the FAA needs. My understanding is they don't need the "Amateur-Built Fabrication and Assembly Checklist" because Van's RV-10 is listed in their list of kits which satisfy the 50%+ rule, but please let me know if anyone has experience FAA asking for the checklist. I have also sent emails to my FSDO and MIDO with a question regarding how verbose the builder's log needs to be. I will write back to this thread if/when the FAA responds.