You have not produced facts to prove your case.
Let me rephrase so you understand.
Investment firms send reports of taxable activity to the IRS.
The same firm sends reports to the investor signaling a taxable event and how much money is involved.
Should my tax return or anyone else’s return differ from the reports the IRS has received regarding income or capital gains, or any other taxable event, you are likely to be questioned about the disparity.
Gathering those reports in some cases is a chore. You always have the option of going to the IRS and asking for what they have in your file for the year in question.
What is owed is as clear as the IRS can make it, which in many cases is not clear, but I and the CPA make my tax return match what the IRS has for data in their possession.
the real reason you seem to be confused is you apparently don’t understand that underlying stocks in a mutual fund are constantly being bought and sold, and that is a taxable event for investors in the fund. The investor hasn’t sold his shares in the fund, but the firm has sold their position, which triggers taxes for investors.
This is one reason ETF’s have become popular due to better tax efficiency for the individual investor. Tax efficiency is about to go out the window for everyone if this idea of taxing unrealized capital gains is allowed to gain traction much less pass into law.
That is different from your original post..of course any assets sold are subject to capital gains. The law being presented has nothing to do with that. You need to understand...you have managers you pay to manage your funds..they represent you. When they sell your stocks contained within your fund you are responsible for paying taxes on gains. Conversely if you lost money on some you can write that off the gain...