I can confirm and clarify this bug a little. Here are the steps I followed when figuring out if this is a bug.
1. I created a test world in 1.7.3 and built two enclosed 5x5 pads of farmland and planted them with potatoes.
2. I spawned two farmer villagers on one of the pads
3. I reloaded the game into 14w04b and spawned two farmer villagers on the other pad.
The villagers created in 1.7.3 broke the crops as they matured but did not appear to pick up the drops and they didn't replant either.
The villagers created in the snapshot functioned correctly.
Upon placing doors nearby only the villagers created in the snapshop would breed. Though if you trade with the legacy villagers they then also became willing to breed, however they still would not plant crops of pick up items.
I can confirm and clarify this bug a little. Here are the steps I followed when figuring out if this is a bug.
1. I created a test world in 1.7.3 and built two enclosed 5x5 pads of farmland and planted them with potatoes.
2. I spawned two farmer villagers on one of the pads
3. I reloaded the game into 14w04b and spawned two farmer villagers on the other pad.
The villagers created in 1.7.3 broke the crops as they matured but did not appear to pick up the drops and they didn't replant either.
The villagers created in the snapshot functioned correctly.
Upon placing doors nearby only the villagers created in the snapshop would breed. Though if you trade with the legacy villagers they then also became willing to breed, however they still would not plant crops of pick up items.