I am in process of building my own new home. I installed 2000 sq ft of white oak in alternating widths of 3", 4" and 5". The T & G lumber I used was cut 3 years ago, air dried for 3 months and then kiln dried to 7%. After that I dry stacked it in the home under construction and it remained there for 2 years with the inside temps maintained at 60 F. At that point I installed it over my sub floor of advantech and a paper barrier. I was careful to maintain a very tight installation with appropriate edge wall expansion gaps. I used staples and probably for sure way over-nailed it (anal on my own home!). At that point I did not finish or sand. I continued to work on the house for another 10 months whic brings me to today. Here is the situation I need advice on;
The floor now has plenty of gaps between boards. They just appeared in the past 3 months. I am now planning to sand and finish. My thought was after a 36 grit pass I would do a Full trowel fill and then finish the sanding steps and finally stain or just poly. However logic (or in experience) tells me that if I full fill and the season changes and the floors boards expand and close the gaps-wouldnt that squeeze the filler out? And consequently if I don't full fill and just sand and finish with the current gaps....wouldn't that look like a poorly done job? And once again what would happen to the poly once the floor expanded in the summer months? I have talked to several installers and received opinions in every direction. So since this is my own dream home and the last one in my life....I sure want to do it the best way possible.
I live in Nashville, TN. IM Jim and thanks for your help

I would do it your way - Full trowel fills and then finish the sanding steps and finally stain or poly. You should be good if using professional filler.

Some floor contractor has tried adding glue to the pre-made filler. I suppose this may help the filler stay in place when the flooring shrinks again next year.