Must admit I'm not quite sure what Lance or NLUK are trying to say here.
If mgf has two classes of ordinary share, A and B, both equivalent in all but name and him and his spouse have 50 shares each, then they do indeed have a 50/50 split of the company shareholding.
As they are technically two different classes of share, then dividends can be paid out on one class but not the other.
AFAICT, the main risk arises where, for example, you've paid £x dividends to take you up to the higher rate threshold but your spouse still has unused basic rate allowance so you pay a dividend out on their class of share only to use up the rest of their basic rate amount. I'm not sure if HMRC have actually challenged the use of alphabet shares in this way as they have with waivers so I'm unsure of the exact details, but as has been pointed out this is something to be wary of and it is on HMRC's radar.
If you're using alphabet shares to pay yourself in the usual way but *restrict* the amount of dividends your spouse receives (because you don't want to go over the £5k dividend allowance, for example), rather than increase the amount they receive, I'm not sure this is an issue and is probably the approach being recommended by accountants in response to the new dividend tax. You could limit your spouse's dividends to £5k but still enable them to own half of the company which could have further tax benefits in the future (e.g. double the CGT allowance on any capital gain on liquidation).
I'm not standing up as an advocate for alphabet shares here, just that I think it can be a valid approach in some circumstances (but you should absolutely get professional advice as there is scope for making a mess of this).