Partner's average shape is actually 4=3=3=3 (actually 4.3=2.7=3=3), his average HCP count 6.3. Without unusual shape, his hand will be likely to make you a heart game only when it contains four-card heart support or a non-spade queen. If he is an aggressive bidder, any hand that fits that description is very likely to bid after your heart opening. If he doesn't have that, hearing from the opponents in spades would not be unusual.
A good test of whether a marginal hand is a 2C opening is whether a decent-fitting yarborough would make game cold. Here, it woudln't. Oppposite a 4=3=3=3 zero count you have to lose a trick in each suit besides spades, and you will go down if trump are even one of your suits fails to break. Opposite 4=3=4=2, you probably need 3-2 hearts and diamonds, and non-horrible clubs. That hand has trouble in diamonds because there's no entry to his hand. With 5=2=4=2, there's almost no chance unless partner has a non-spade queen.
In short, if the auction goes 1H - all pass, you're likely to be pretty darned happy.
If you open 2C and partner has a hand that would have passed your 1H bid, you're likely to have something like this auction: 2C - 2D (I'm assuming that's negative in your methods); 2H, and then:
- with three-card heart support, 3H -- but you have no idea what you can make;
- with long spades, 2S; then probably 3C by you; now what will you do if he bids 3D -- you probably can't make five -- or 3H -- that's probably just a doubleton, and you will probably pass;
- with no five-card suit and no heart support, 2NT; now, depending on your methods, you may get to play three of a minor or just get too high.
I you play 2H negative, 2D waiting, it will start 2C - 2H; 3H and you will be passed there a lot of the time of the time, raised a lot of the rest -- but when raised, it will be wrong a lot. Or you could judge to pass his 2H bid, gaining nothing over the 1H opening.
It is not wrong to consider what happens opposite a really bad hand, because that really bad hand is the reason you're reluctant to open a lowly 1H.
Granted, the times partner has xxxx Qx JTxx xx, you'll miss a good game. Basically, you're unhappy opening 1H when partner has a working queen but almost nothing else, unhappy or ambivalent otherwise.
Of course, open 2C and you'll miss your slam when partner holds Jxxx Qx Qxxxx Jx (2C-2NT; 4H - P or several other possibilities all of which end in game), while instead it could go 1H - 1S; 3C - 3H; 4D - 5D; 6D. You'll also find the slam with the partenr's minors reversed, while you're moderately likely to miss it after a 2C opening.
Monstrously strong three-suiters are one of the reasons to play precision, because patterning out after a 2C opening requires the assumption that partner is not broke, which is often incorrect.