Jhana doesn't require to achieve first stage of stream entry - but it helps build concentration fast so in some Burmese Vipassana tradition, mediators are train

Jhana doesn't require to achieve first stage of stream entry - but it helps build concentration fast so in some Burmese Vipassana tradition, mediators are trained in to achieve just enough samahta and move to Vipassana. Just to the point of strong samadhi and then switch to Vipassana.(Mahasi) But in a few meditation center, first jhana needed to be attained to switch to Vipassana ( Thel inn guu and Paa Out traditions) . In one rare meditation tradition (Maung Htaung Myay Sinn), all four Rupa Jhana is trained till attained first and paractioners are given exercises and experiment with Jhana (45 days 8 hr a day meditation retreat with 30 days are full on Samahta and Jhana practices, then moves to Vipassana). Reasons for not going fully into jhana in traditions like mahasi is because Jhana practices have addicting qualities and paractioners will be dwelled unto that. And those with addictive personality would not let go of jhana and won't practice Vipassana.