My boat had wire to rope halyards that, which I found out when replacing, were not spliced together but rather knotted to a loop on the wire. That could be the reason for your knot. Besides minimal stretch, wire was needed because the masthead sheave is too narrow for 3/8" line.... in fact it is just a little over 1/4"... Anyway, I found it impossible to remove the exit block box on the port side to remove the knot.....luckily I was able to get the starboard(main halyard) side loose and picked it out with a piece of wire.
Btw, you should lubricate the masthead sheaves when you go up. To be sure, check the diameter of the sheave's groove... the owner's manual has a diagram showing it's dimensions... yours may have been converted since it's 10 years younger than my boat. You want the halyard to run freely through the sheave.... makes hoisting and dropping the sails a heck of a lot easier.
Anyway.... the sheave width issue is important in deciding what size line you'll use for the halyard.. You can always replace with a pre-made wire to rope halyard, nothing wrong with that. I chose to build my own "tapered" halyard. I used a 3/16" dyneema core (samson amsteel) and covered the back half, the part that is handled and cleated, with a 5/16" sheath. The dyneema is stronger than steel. The cover is inexpensive dacron/polyester line with the core removed. In fact, I uses the core of the Samson LS to fish the new dyneema core into place. There is a simple splice, called a "bury" or splice that creates the "taper" where the cover is buried into the core. It looks pretty cool, and is super strong with NO stretch. You can splice an eye in the dyneema core's single braid... really easy splice btw. but the last one I made I just tied a halyard knot to the captive pin "D" shackle.