Shape of 羊 radical does not match the evidence, but it appears that Vietnam convention is to use the straight 羊 radical (e.g. U+7F9D 羝, U+2636B 𦍫, U+263AC 𦎬, U+2B155 𫅕, and WS217-03523 V-F1AE0; but note that U+7FB6 羶 has a bent ⺶ radical).

#4646 is a valid observation. The NomNaTong font contains 44 characters with 羊 as an immediate component (not counting 羊 as a component of another component character). All except for 2, U+2637A and U+7FB6 use 羊 with a straight stroke. If any change were to be made, we would probably normalize U+2637A and U+7FB6 to straight 羊.