So you tend not to open 1d with 4 cards in balanced hands. Its reasonably common to have two clubs for a 1c opener. 4d is COG, so it looks like partner is 4-6. It didn't seem right to play in a 4-3 heart fit with a spade tap likely coming, when partner might have good enough clubs for 5C.
Now answer the poll questions:
Other things I dont understand: How is this sequence different from bidding 4C over 1S when it comes back, that is surely 4-6 and GF. Why did partner not double 3S? Isnt that what you should always do if you care about whether partner has natural clubs. If partner does not have 4+ clubs he just bids 4H? Bidding 4C might then already show 6, and presumeably a worry about passing 3Sx. Does that indicate a slam try with a spade void?