You are reading the datasheet wrong. Yes, the BU4S66G2 has an on resistance of typ. 500 ohms, max 600 ohms at 5V Vdd but at 5V Vdd a T.I. CD4066 has an on resistance of typ. 470 ohms, max. 1050 ohms, so at best is fractionally better but is quite likely to be significantly worse. Anyway why do you care about the on resistance at 5V Vdd when your supply is 13V? You probably should be averaging the 10V and 15V typ. on resistances from the datasheets for a typ. value near 13V and using the 10V max. on resistance for worst case design.
Also, what's wrong with using an ordinary 4066, even if 3/4 of it isn't needed? If you need a lower on resistance, parallel channels. With the current supply chain issues, using a 'jellybean' widely second sourced part could save you a lot of grief vs designing in a single source specialist part, then when it suddenly goes out of stock, running around trying to find a pin compatible replacement and probably having to pay through the nose for it, or having to source parts of dubious provenance, that have been improperly stored, from a parts scalper.
Also your hate-on for DG-series parts is irrational - some are only slightly more expensive than the BU4S66G2 you are looking at with vastly superior performance.
Here's a Mouser parametric search with five options under £1:
https://mou.sr/3v2OSqn