I guess I was not able to explain properly my point, that's way it appears as ancillary.
What Sam remarked is that "This [bolt size] seems too large for such a small tank.".
For long time, Table 5.21 imposed considerable uplift giving bolts' and foundation oversizing vs. common sense. In case the tank has a frangible roof, that is- the criterion "3*pf" is what you need to consider.
In case the tank is not designed by API 650/5.10.2.6 d., of course the uplift associated to frangibility must be removed- as you said you decided to proceed in 2017 edn. I would remark that your competitor- former e-tank- made this criterion as "non-applicable" for non-frangible long time ago. In fact, today it is the same note as in the edition 11th of API 650 "Frangibility pressure applies only to tanks designed to 5.10.2.6 d", that's why an ancillary discussion would be which is the factor that made you to remove "3*pf" frangibility criteria just now.
What is new is that also criterion "1.5*pf" is withdrawn. This criterion was also a source of oversizing bolts and foundation. Since you said you plan to keep it, I just hope shall be removed as soon as possible.