Amongst the first things I do when I receive a new Martin - I’ve owned five, a D-35, J-40, OM-28 Marquis, HD-28V, and a D-18 - is dump the POS soft plastic pins that all but the OM-28 Marquis were fitted with, ream and slot the bridge-pin holes and install solid, un-slotted pins (either ebony or Antique Acoustics galalith a.k.a. ‘hard plastic’). I do this to protect and extend the life of the bridge-plate, and achieve improved tuning stability.

I have never experienced any tonal change from replacing bridge-pins, whatever material(s) have been involved, and I’m convinced that there’s a great deal of confirmation-bias involved when others claim to have achieved an almost-miraculous transformation in their guitar’s tone, and wax lyrical about ‘choirs of angels’ and such nonsense.

I currently have ebony pins in the D-18 and Antique Acoustics in the HD-28V, which are my two remaining Martins, and I have no plans to change - if I did, it would definitely not be to ‘liquid metal’ pins. Over-hyped and over-priced AFAIC.

As always, the standard disclaimer applies - IMHO. However, I realise that YMMV, and that’s fine by me.