In 2018 with the adoption of accounting standards Update number 2016-01 issued by the FASB....it required companies to include UNREALIZED Gains and losses from equity investments in their net income.
Comparisons to a period when Berkshire could record those gains or loses in comprehensive income--to me are not useful ( I like the old rules better, so does Waren but...)

You may have misunderstood the accounting change. It had absolutely no effect on book value, only reported EPS. It changed only the line item on which the change was placed: either the earnings line, or the change to comprehensive income. Unrealized gains and losses were always counted in book.

The TCJA, on the other hand, did cause a big one time change in reported book value because the lower tax rates reduced the estimated tax liability from unrealized gains. But it was largely counteracted by the change in TRUE value due to the lower future tax rates. Trying to estimate the relative size of these two changes is extremely subtle, but in general they cancel out, and P/B remains as accurate as a valuation metric as it ever was.

Note, I don't just *assume* that is the case. I do a number of more sophisticated valuation exercises as well, and so far, more or lees by coincidence, the two still match. P/B is so far, as good as it ever was.

Jim