Your link 1 specifically says the opposite, >Held-to-maturity debt securities are reported at amortized cost. This is due to the securities being held to colle

Your link 1 specifically says the opposite, >Held-to-maturity debt securities are reported at amortized cost. This is due to the securities being held to collect contractual cash flows. As such, it would not be appropriate for an investor to recognize interim fluctuations in fair value through a fair value model since those fluctuations will not be realized by the investor. That is, HTM debt are not reported at fair value in GAAP. The fair value in that case would be the mark to market value (provided sufficient liquidity). The LCR requires HQLA be valued at fair value. I think the confusion here is that HTM securities are in fact treated differently when calculating capital adequacy requirements, which are not the same as LCR! Your second link (which btw predates the start of LCR in the US) is about capital adequacy requirements.