It is. Tiers 1-3 never had any restrictions on leaving home or staying away from home. You can check the links in the wiki, this was all documented at the time by me on this thread.

Those links refer to guidelines not the law.

EDIT: I think the confusion here is between two restrictions:
1. A restriction on you that you could not stay away from home overnight, this was never in the tier system but we did have this during June 2020. this would prevent you staying away from home overnight which includes staying away within the UK or outside,
2. A restriction on hotels taking guests for leisure/holiday stays, we did have this in tiers 3 & 4 (apologies I may have just said tier 4 earlier) and it was the restriction on the hotels not on the individual.

Based on what has been reported it seems from 29 March stay at home will be revoked, but instead we will have 1 just as happened last year. I think staying away from home, both within the UK or abroad is unlikely until April at the earliest, i.e. we will have 1 for at least 4-5 weeks before it is relaxed further.