you are correct Allan, Pb ratios needs to be corrected with NIST614 as WC-1 have very variable lead values. Some use NIST614 for everything, while others do a mix of NIST614 and WC-1.
From Drost et al., 2018:
NIST 614 standard glass is used as the primary reference material for calibration of both the elemental concentration data and the U-Pb isotope data.
From Roberts et al., 2017:
"Normalization uses a standard-sample bracketing protocol. First, NIST614 is used for mass fractionation correction of Pb isotope ratios, which on the instrument at NIGL is ca. 0.7% for the 207Pb/206Pb ratio. Second, the WC-1 calcite is used for correction of U-Pb ratios (as described in Li et al.  and Roberts and Walker ; see Appendix Appendix A)."