Yeah I think it's a combination of the unstressed final syllable and that particular consonant cluster at the end of 'text'. If the vowel in the final syllable gets reduced to schwa or perhaps deleted altogether (which is common in final unstressed syllables), then you end up with a /kstd/ sequence which isn't permissible in English as it's too many consonant sounds together.
You'd have to hear it in context to know it was a sound change and not a vivid past stylistic thing though - you'd want to hear the speaker using other pasts in proximity to it to rule that out.
It might be influenced by a sound analogy with other past forms too, because /ksd/ is a common sequence at the end of a whole bunch of past forms (like 'mixed', hexed' etc).