While I’m sympathetic to his general argument, I think there are some significant differences under present conditions that require serious thinking about the revival of an analogous strategy.
Firstly, the existence of large reformist parties with working class roots (eg, present-day European social democracy) that will continue to win a significant section of workers. This is quite unlike the rapidly growing SPD at the beginning of the 20th century. Moreover, once a party has grown to significance, there will be pressures from the electorate and members to enter into coalitions for important short-term reforms and keeping the reformist party in check. Anything else is considered ‘irresponsible’. Look at the present-day Norwegian Socialist Left Party, for example.